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

[Stefan Gränitz via cfe-commits]

weliveindetail wrote:

Thanks for your note. Looks like the problem is that the ARM target is not registered. It's an uncommon requirement for a unitttest.. Will see how to check that at runtime. If you have an idea, let me know. Thanks

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