[clang] [clang-repl] Factor out CreateJITBuilder() and allow specialization in derived classes (PR #84461)

[Stefan Gränitz via cfe-commits]

weliveindetail wrote:

I will try this https://github.com/llvm/llvm-project/blob/release/18.x/llvm/unittests/DebugInfo/LogicalView/CodeViewReaderTest.cpp#L482 and push a quick-fix.

https://github.com/llvm/llvm-project/pull/84461