Fixed compilation errors on gcc. #12

Job	Run time
format	15s
build (gcc, Debug, OpenGL)	3m 12s
build (gcc, Debug, Vulkan)	3m 25s
build (gcc, Release, OpenGL)	3m 51s
build (gcc, Release, Vulkan)	3m 51s
build (clang, Debug, OpenGL)	2m 43s
build (clang, Debug, Vulkan)	2m 52s
build (clang, Release, OpenGL)	3m 47s
build (clang, Release, Vulkan)	3m 52s
build (android-clang, Debug, OpenGL)	2m 38s
build (android-clang, Debug, Vulkan)	3m 36s
build (android-clang, Release, OpenGL)	3m 42s
build (android-clang, Release, Vulkan)	3m 55s
	41m 39s

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