Add llvm_path #36

Job	Run time
Ubuntu / Release / gcc	22m 11s
macOS / Release / homebrew-clang	8m 36s
Windows / Release / cl	25m 56s
Ubuntu / Debug / gcc	18m 4s
Ubuntu / Release / clang	19m 22s
Windows / Release / clang	35m 48s
macOS / Debug / homebrew-clang	5m 57s
Ubuntu / Debug / clang	15m 12s
Windows / Release / clang-cl	29m 12s
macOS / Release / system-clang	5m 33s
Windows / Debug / cl	24m 32s
macOS / Debug / system-clang	5m 25s
Windows / Debug / clang	27m 23s
Windows / Debug / clang-cl	26m 23s
	4h 29m 34s

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