JIT

gh-138451: Support custom LLVM installation path #3966

Job	Run time
Interpreter (Debug)	9m 35s
x86_64-pc-windows-msvc/msvc (Release)	13m 54s
i686-pc-windows-msvc/msvc (Debug)	22m 47s
i686-pc-windows-msvc/msvc (Release)	14m 4s
x86_64-apple-darwin/clang (Release)	15m 59s
x86_64-pc-windows-msvc/msvc (Debug)	21m 57s
x86_64-apple-darwin/clang (Debug)	21m 30s
aarch64-pc-windows-msvc/msvc (Release)	19m 13s
aarch64-apple-darwin/clang (Release)	9m 45s
aarch64-apple-darwin/clang (Debug)	13m 0s
aarch64-pc-windows-msvc/msvc (Debug)	25m 15s
aarch64-unknown-linux-gnu/gcc (Debug)	6m 58s
x86_64-unknown-linux-gnu/gcc (Debug)	11m 27s
aarch64-unknown-linux-gnu/gcc (Release)	5m 55s
x86_64-unknown-linux-gnu/gcc (Release)	7m 29s
	3h 38m 48s

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