JIT

gh-134273: Allow setting JIT compiler flags with `CFLAGS_JIT` #3620

Job	Run time
Interpreter (Debug)	9m 58s
i686-pc-windows-msvc/msvc (Debug)	23m 52s
i686-pc-windows-msvc/msvc (Release)	14m 38s
x86_64-pc-windows-msvc/msvc (Debug)	20m 52s
x86_64-pc-windows-msvc/msvc (Release)	10m 47s
aarch64-pc-windows-msvc/msvc (Debug)	24m 31s
aarch64-pc-windows-msvc/msvc (Release)	18m 52s
x86_64-apple-darwin/clang (Debug)	15m 27s
x86_64-apple-darwin/clang (Release)	12m 0s
aarch64-apple-darwin/clang (Debug)	11m 42s
aarch64-apple-darwin/clang (Release)	11m 2s
x86_64-unknown-linux-gnu/gcc (Debug)	10m 24s
x86_64-unknown-linux-gnu/gcc (Release)	6m 36s
aarch64-unknown-linux-gnu/gcc (Debug)	7m 43s
aarch64-unknown-linux-gnu/gcc (Release)	5m 57s
	3h 24m 21s

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