Index: build/premake/extern_libs5.lua
===================================================================
--- build/premake/extern_libs5.lua
+++ build/premake/extern_libs5.lua
@@ -315,7 +315,7 @@
 			else
 				-- Support GLOOX_CONFIG for overriding the default (pkg-config --cflags gloox)
 				-- i.e. on OSX where it gets set in update-workspaces.sh
-				pkgconfig.add_includes("gloox", os.getenv("GLOOX_CONFIG"))
+				pkgconfig.find_system("gloox", os.getenv("GLOOX_CONFIG")).add_includes()
 			end
 		end,
 		link_settings = function()
@@ -326,7 +326,7 @@
 					no_delayload = 1,
 				})
 			else
-				pkgconfig.add_links("gloox", os.getenv("GLOOX_CONFIG"))
+				pkgconfig.find_system("gloox", os.getenv("GLOOX_CONFIG")).add_links()
 
 				if os.istarget("macosx") then
 					-- Manually add gnutls dependencies, those are not present in gloox's pkg-config
@@ -383,7 +383,7 @@
 			else
 				-- Support ICU_CONFIG for overriding the default (pkg-config --cflags icu-i18n)
 				-- i.e. on OSX where it gets set in update-workspaces.sh
-				pkgconfig.add_includes("icu-i18n", os.getenv("ICU_CONFIG"), "--cppflags")
+				pkgconfig.find_system("icu-i18n", os.getenv("ICU_CONFIG")).add_includes("--cppflags")
 			end
 		end,
 		link_settings = function()
@@ -395,7 +395,7 @@
 					no_delayload = 1,
 				})
 			else
-				pkgconfig.add_links("icu-i18n", os.getenv("ICU_CONFIG"), "--ldflags-searchpath --ldflags-libsonly --ldflags-system")
+				pkgconfig.find_system("icu-i18n", os.getenv("ICU_CONFIG")).add_links("--ldflags-searchpath --ldflags-libsonly --ldflags-system")
 			end
 		end,
 	},
@@ -462,7 +462,7 @@
 			else
 				-- Support XML2_CONFIG for overriding the default (pkg-config --cflags libxml-2.0)
 				-- i.e. on OSX where it gets set in update-workspaces.sh
-				pkgconfig.add_includes("libxml-2.0", os.getenv("XML2_CONFIG"))
+				pkgconfig.find_system("libxml-2.0", os.getenv("XML2_CONFIG")).add_includes()
 			end
 			if os.istarget("macosx") then
 				-- libxml2 needs _REENTRANT or __MT__ for thread support;
@@ -479,7 +479,7 @@
 					links { "libxml2" }
 				filter { }
 			else
-				pkgconfig.add_links("libxml-2.0", os.getenv("XML2_CONFIG"))
+				pkgconfig.find_system("libxml-2.0", os.getenv("XML2_CONFIG")).add_links()
 			end
 		end,
 	},
@@ -570,14 +570,14 @@
 			elseif not _OPTIONS["android"] then
 				-- Support SDL2_CONFIG for overriding the default (pkg-config sdl2)
 				-- i.e. on OSX where it gets set in update-workspaces.sh
-				pkgconfig.add_includes("sdl2", os.getenv("SDL2_CONFIG"))
+				pkgconfig.find_system("sdl2", os.getenv("SDL2_CONFIG")).add_includes()
 			end
 		end,
 		link_settings = function()
 			if os.istarget("windows") then
 				add_default_lib_paths("sdl2")
 			elseif not _OPTIONS["android"] then
-				pkgconfig.add_links("sdl2", os.getenv("SDL2_CONFIG"))
+				pkgconfig.find_system("sdl2", os.getenv("SDL2_CONFIG")).add_links()
 			end
 		end,
 	},
@@ -585,7 +585,16 @@
 		compile_settings = function()
 			if _OPTIONS["with-system-mozjs"] then
 				if not _OPTIONS["android"] then
-					pkgconfig.add_includes("mozjs-78")
+					-- Many linux distros package icu headers in with spidermonkey headers, but
+					-- do not provide compatible icu library files to go along with them.
+					--
+					-- Attempting to use the spidermonkey-icu headers with a distro's
+					-- standard-icu lib files causes linking errors.
+					--
+					-- Therefore, we set the spidermonkey includes directory to be searched
+					-- *after* the standard system includes so gcc/clang finds and includes
+					-- compatible icu headers.
+					pkgconfig.find_system("mozjs-78").add_includes_after_system()
 				end
 			else
 				if os.istarget("windows") then
@@ -607,7 +616,7 @@
 				if _OPTIONS["android"] then
 					links { "mozjs-78" }
 				else
-					pkgconfig.add_links("mozjs-78")
+					pkgconfig.find_system("mozjs-78").add_links()
 				end
 			else
 				filter { "Debug", "action:vs*" }
@@ -674,7 +683,7 @@
 				-- wxwidgets does not come with a definition file for pkg-config,
 				-- so we have to use wxwidgets' own config tool
 				wx_config_path = os.getenv("WX_CONFIG") or "wx-config"
-				pkgconfig.add_includes(nil, wx_config_path, "--unicode=yes --cxxflags")
+				pkgconfig.find_system(nil, wx_config_path).add_includes("--unicode=yes --cxxflags")
 			end
 		end,
 		link_settings = function()
@@ -682,19 +691,19 @@
 				libdirs { libraries_dir.."wxwidgets/lib/vc_lib" }
 			else
 				wx_config_path = os.getenv("WX_CONFIG") or "wx-config"
-				pkgconfig.add_links(nil, wx_config_path, "--unicode=yes --libs std,gl")
+				pkgconfig.find_system(nil, wx_config_path).add_links("--unicode=yes --libs std,gl")
 			end
 		end,
 	},
 	x11 = {
 		compile_settings = function()
 			if not os.istarget("windows") and not os.istarget("macosx") then
-				pkgconfig.add_includes("x11")
+				pkgconfig.find_system("x11").add_includes()
 			end
 		end,
 		link_settings = function()
 			if not os.istarget("windows") and not os.istarget("macosx") then
-				pkgconfig.add_links("x11")
+				pkgconfig.find_system("x11").add_links()
 			end
 		end,
 	},
Index: build/premake/pkgconfig/pkgconfig.lua
===================================================================
--- build/premake/pkgconfig/pkgconfig.lua
+++ build/premake/pkgconfig/pkgconfig.lua
@@ -1,11 +1,11 @@
 local m = {}
-m._VERSION = "1.1.0-dev"
+m._VERSION = "1.2.1-dev"
 
 local function os_capture(cmd)
 	return io.popen(cmd, 'r'):read('*a'):gsub("\n", " ")
 end
 
-function m.add_includes(lib, alternative_cmd, alternative_flags)
+local function find_includes(lib, alternative_cmd, alternative_flags)
 	local result
 	if not alternative_cmd then
 		result = os_capture("pkg-config --cflags "..lib)
@@ -17,9 +17,10 @@
 		end
 	end
 
-	-- Small trick: delete the space after -include so that we can detect
-	-- which files have to be force-included without difficulty.
+	-- Small trick: delete the space after -include and -isystem so that
+	-- we can detect which files have to be included without difficulty.
 	result = result:gsub("%-include +(%g+)", "-include%1")
+	result = result:gsub("%-isystem +(%g+)", "-isystem%1")
 
 	local dirs = {}
 	local files = {}
@@ -27,6 +28,8 @@
 	for w in string.gmatch(result, "[^' ']+") do
 		if string.sub(w,1,2) == "-I" then
 			table.insert(dirs, string.sub(w,3))
+		elseif string.sub(w,1,8) == "-isystem" then
+			table.insert(dirs, string.sub(w,9))
 		elseif string.sub(w,1,8) == "-include" then
 			table.insert(files, string.sub(w,9))
 		else
@@ -34,12 +37,10 @@
 		end
 	end
 
-	sysincludedirs(dirs)
-	forceincludes(files)
-	buildoptions(options)
+	return dirs, files, options
 end
 
-function m.add_links(lib, alternative_cmd, alternative_flags)
+local function find_links(lib, alternative_cmd, alternative_flags)
 	local result
 	if not alternative_cmd then
 		result = os_capture("pkg-config --libs "..lib)
@@ -69,9 +70,35 @@
 		end
 	end
 
-	links(libs)
-	libdirs(dirs)
-	linkoptions(options)
+	return libs, dirs, options
+end
+
+function m.find_system(lib, alternative_cmd)
+
+	local meths = {}
+
+	function meths.add_includes(alternative_flags)
+		local dirs, files, options = find_includes(lib, alternative_cmd, alternative_flags)
+		sysincludedirs(dirs)
+		forceincludes(files)
+		buildoptions(options)
+	end
+
+	function meths.add_includes_after_system(alternative_flags)
+		local dirs, files, options = find_includes(lib, alternative_cmd, alternative_flags)
+		aftersysincludedirs(dirs)
+		forceincludes(files)
+		buildoptions(options)
+	end
+
+	function meths.add_links(alternative_flags)
+		local libs, dirs, options = find_links(lib, alternative_cmd, alternative_flags)
+		links(libs)
+		libdirs(dirs)
+		linkoptions(options)
+	end
+
+	return meths
 end
 
 return m
Index: build/premake/premake5/modules/gmake/gmake_cpp.lua
===================================================================
--- build/premake/premake5/modules/gmake/gmake_cpp.lua
+++ build/premake/premake5/modules/gmake/gmake_cpp.lua
@@ -521,7 +521,7 @@
 
 
 	function make.includes(cfg, toolset)
-		local includes = toolset.getincludedirs(cfg, cfg.includedirs, cfg.sysincludedirs)
+		local includes = toolset.getincludedirs(cfg, cfg.includedirs, cfg.sysincludedirs, cfg.aftersysincludedirs)
 		_p('  INCLUDES +=%s', make.list(includes))
 	end
 
Index: build/premake/premake5/modules/gmake2/gmake2_cpp.lua
===================================================================
--- build/premake/premake5/modules/gmake2/gmake2_cpp.lua
+++ build/premake/premake5/modules/gmake2/gmake2_cpp.lua
@@ -436,7 +436,7 @@
 
 
 	function cpp.includes(cfg, toolset)
-		local includes = toolset.getincludedirs(cfg, cfg.includedirs, cfg.sysincludedirs)
+		local includes = toolset.getincludedirs(cfg, cfg.includedirs, cfg.sysincludedirs, cfg.aftersysincludedirs)
 		p.outln('INCLUDES +=' .. gmake2.list(includes))
 	end
 
Index: build/premake/premake5/src/_premake_init.lua
===================================================================
--- build/premake/premake5/src/_premake_init.lua
+++ build/premake/premake5/src/_premake_init.lua
@@ -18,6 +18,13 @@
 --
 -----------------------------------------------------------------------------
 
+	api.register {
+		name = "aftersysincludedirs",
+		scope = "config",
+		kind = "list:directory",
+		tokens = true,
+	}
+
 	api.register {
 		name = "architecture",
 		scope = "config",
Index: build/premake/premake5/src/tools/clang.lua
===================================================================
--- build/premake/premake5/src/tools/clang.lua
+++ build/premake/premake5/src/tools/clang.lua
@@ -168,10 +168,10 @@
 --    An array of symbols with the appropriate flag decorations.
 --
 
-	function clang.getincludedirs(cfg, dirs, sysdirs)
+	function clang.getincludedirs(cfg, dirs, sysdirs, aftersysdirs)
 
 		-- Just pass through to GCC for now
-		local flags = gcc.getincludedirs(cfg, dirs, sysdirs)
+		local flags = gcc.getincludedirs(cfg, dirs, sysdirs, aftersysdirs)
 		return flags
 
 	end
Index: build/premake/premake5/src/tools/gcc.lua
===================================================================
--- build/premake/premake5/src/tools/gcc.lua
+++ build/premake/premake5/src/tools/gcc.lua
@@ -239,7 +239,7 @@
 -- Decorate include file search paths for the GCC command line.
 --
 
-	function gcc.getincludedirs(cfg, dirs, sysdirs)
+	function gcc.getincludedirs(cfg, dirs, sysdirs, aftersysdirs)
 		local result = {}
 		for _, dir in ipairs(dirs) do
 			dir = project.getrelative(cfg.project, dir)
@@ -249,6 +249,10 @@
 			dir = project.getrelative(cfg.project, dir)
 			table.insert(result, '-isystem ' .. p.quoted(dir))
 		end
+		for _, dir in ipairs(aftersysdirs or {}) do
+			dir = project.getrelative(cfg.project, dir)
+			table.insert(result, '-idirafter ' .. p.quoted(dir))
+		end
 		return result
 	end
 
Index: build/premake/premake5/src/tools/msc.lua
===================================================================
--- build/premake/premake5/src/tools/msc.lua
+++ build/premake/premake5/src/tools/msc.lua
@@ -217,13 +217,17 @@
 -- Decorate include file search paths for the MSVC command line.
 --
 
-	function msc.getincludedirs(cfg, dirs, sysdirs)
+	function msc.getincludedirs(cfg, dirs, sysdirs, aftersysdirs)
 		local result = {}
 		dirs = table.join(dirs, sysdirs)
 		for _, dir in ipairs(dirs) do
 			dir = project.getrelative(cfg.project, dir)
 			table.insert(result, '-I' ..  p.quoted(dir))
 		end
+		for _, dir in ipairs(aftersysdirs) do
+			dir = project.getrelative(cfg.project, dir)
+			table.insert(result, '/INCLUDE:"' .. dir .. '"')
+		end
 		return result
 	end
 
Index: build/premake/premake5/tests/tools/test_gcc.lua
===================================================================
--- build/premake/premake5/tests/tools/test_gcc.lua
+++ build/premake/premake5/tests/tools/test_gcc.lua
@@ -619,6 +619,17 @@
 	end
 
 
+--
+-- Check handling of search paths that come after the standard system search paths
+--
+
+	function suite.includeDirs_onAfterSysIncludeDirs()
+		aftersysincludedirs { "/usr/local/include" }
+		prepare()
+		test.contains("-idirafter /usr/local/include", gcc.getincludedirs(cfg, cfg.includedirs, cfg.sysincludedirs, cfg.aftersysincludedirs))
+	end
+
+
 --
 -- Check handling of link time optimization flag.
 --
Index: source/scriptinterface/ScriptTypes.h
===================================================================
--- source/scriptinterface/ScriptTypes.h
+++ source/scriptinterface/ScriptTypes.h
@@ -82,7 +82,7 @@
 #endif
 
 #if MOZJS_MINOR_VERSION != 6
-#error Your compiler is trying to use an untested minor version of the \
+#warning Your compiler is trying to use an untested minor version of the \
 SpiderMonkey library. If you are a package maintainer, please make sure \
 to check very carefully that this version does not change the behaviour \
 of the code executed by SpiderMonkey. Different parts of the game (e.g. \