JIT

gh-138451: Support custom LLVM installation path #3959

Job	Run time
Interpreter (Debug)	9m 37s
i686-pc-windows-msvc/msvc (Release)	13m 35s
i686-pc-windows-msvc/msvc (Debug)	20m 15s
aarch64-apple-darwin/clang (Debug)	12m 32s
aarch64-pc-windows-msvc/msvc (Release)	18m 7s
aarch64-unknown-linux-gnu/gcc (Release)	5m 39s
aarch64-unknown-linux-gnu/gcc (Debug)	7m 17s
aarch64-apple-darwin/clang (Release)	10m 31s
aarch64-pc-windows-msvc/msvc (Debug)	25m 30s
x86_64-unknown-linux-gnu/gcc (Debug)	10m 38s
x86_64-pc-windows-msvc/msvc (Release)	13m 37s
x86_64-pc-windows-msvc/msvc (Debug)	19m 58s
x86_64-apple-darwin/clang (Release)	20m 22s
x86_64-apple-darwin/clang (Debug)	20m 0s
x86_64-unknown-linux-gnu/gcc (Release)	6m 50s
	3h 34m 28s

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