fix validation layer build #16

Job	Run time
Ubuntu / Release / gcc	20m 19s
macOS / Release / homebrew-clang	3m 27s
Ubuntu / Debug / gcc	16m 16s
macOS / Debug / homebrew-clang	2m 45s
Ubuntu / Release / clang	17m 4s
Windows / Release / cl	30m 15s
macOS / Release / system-clang	2m 49s
Ubuntu / Debug / clang	13m 13s
macOS / Debug / system-clang	2m 12s
Windows / Release / clang	26m 39s
Windows / Release / clang-cl	24m 28s
Windows / Debug / cl	16m 52s
Windows / Debug / clang	24m 7s
Windows / Debug / clang-cl	22m 27s
	3h 42m 53s

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