Index: ps/trunk/libraries/source/spidermonkey/patch.sh
===================================================================
--- ps/trunk/libraries/source/spidermonkey/patch.sh	(revision 27440)
+++ ps/trunk/libraries/source/spidermonkey/patch.sh	(revision 27441)
@@ -1,33 +1,34 @@
 #!/bin/sh
 set -e
 
+OS="${OS:=$(uname -s)}"
 # Apply patches if needed
 # This script gets called from build.sh.
 
 # The rust code is only linked if the JS Shell is enabled,
 # which fails now that rust is required in all cases.
 # https://bugzilla.mozilla.org/show_bug.cgi?id=1588340
 patch -p1 < ../FixRustLinkage.diff
 
 # On windows, we need to differente debug/release library names.
 patch -p1 < ../FixWindowsLibNames.diff
 
 # There is an issue on 32-bit linux builds sometimes.
 # NB: the patch here is Comment 21 modified by Comment 25
 # but that seems to imperfectly fix the issue with GCC.
 # It also won't compile on windows - in doubt, apply only where relevant.
 # https://bugzilla.mozilla.org/show_bug.cgi?id=1729459
 if [ "$(uname -m)" = "i686" ] && [ "${OS}" != "Windows_NT" ]
 then
 	patch -p1 < ../FixFpNormIssue.diff
 fi
 
-if [ "$(uname -s)" = "Darwin" ]
+if [ "$OS" = "Darwin" ]
 then
     # The bundled virtualenv version is not working on MacOS
     # with recent homebrew and needs to be upgraded.
     # Install it locally to not pollute anything.
 	pip3 install --upgrade -t virtualenv virtualenv
     export PYTHONPATH="$(pwd)/virtualenv:$PYTHONPATH"
-    patch -p1 < ../FixVirtualenv.diff
+    patch -p1 < ../FixVirtualEnv.diff
 fi