[clang] [REAPPLY][Clang-Repl] Add support for out-of-process execution. #110418 (PR #144064)

[Abhinav Kumar via cfe-commits]

kr-2003 wrote:

> I just tracked down slowness running clang tests locally to this change. It's very noticeable if I run a single test, or a single directory of tests.

**Proposed work around for this:**
Determining Out-of-Process JIT support once during the Cmake configure step(not runtime), and dump the result into ``lit.site.cfg.py`` as a config variable. This eliminates the overhead but will not work in cross-compilation scenarios where we build for one target and run the tests on a different. Those bot owners will have to manually configure lit for their test environment.


https://github.com/llvm/llvm-project/pull/144064