Simplify update_glslang_sources.py #680

Job	Run time
iOS	39s
emscripten	37s
android (ON)	15s
linux (clang, clang++, Debug)	22s
android (OFF)	15s
Linux Backcompat	39s
linux (clang, clang++, Release)	15s
linux-asan (gcc, g++, Debug, -fsanitize=address)	15s
linux (gcc, g++, Debug)	15s
linux-asan (gcc, g++, Debug, -fsanitize=thread)	1m 54s
linux (gcc, g++, Release)	16s
macos (macos-12, clang, clang++, Debug)	25s
windows (windows-2019, windows, Debug)	20s
macos (macos-12, clang, clang++, Release)	27s
windows (windows-2019, windows, Release)	1m 10s
macos (macos-12, gcc, g++, Debug)	40s
macos (macos-12, gcc, g++, Release)	2m 4s
macos (macos-13, clang, clang++, Debug)	26s
macos (macos-13, clang, clang++, Release)	28s
macos (macos-13, gcc, g++, Debug)	38s
macos (macos-13, gcc, g++, Release)	35s
	12m 55s

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