When building NVTT on raspbian and some other linuxes (I believe @Freagarach reported it too) I get the following warning
CMake Warning (dev) at /usr/share/cmake-3.13/Modules/FindOpenGL.cmake:270 (message): Policy CMP0072 is not set: FindOpenGL prefers GLVND by default when available. Run "cmake --help-policy CMP0072" for policy details. Use the cmake_policy command to set the policy and suppress this warning. FindOpenGL found both a legacy GL library: OPENGL_gl_LIBRARY: /usr/lib/arm-linux-gnueabihf/libGL.so and GLVND libraries for OpenGL and GLX: OPENGL_opengl_LIBRARY: /usr/lib/arm-linux-gnueabihf/libOpenGL.so OPENGL_glx_LIBRARY: /usr/lib/arm-linux-gnueabihf/libGLX.so OpenGL_GL_PREFERENCE has not been set to "GLVND" or "LEGACY", so for compatibility with CMake 3.10 and below the legacy GL library will be used. Call Stack (most recent call first): src/CMakeLists.txt:20 (INCLUDE) This warning is for project developers. Use -Wno-dev to suppress it.