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

[Stefan Gränitz via cfe-commits]

weliveindetail wrote:

We do need the target and not just the symbols. It could be any non-native target, but implementing a selection mechanism isn't worth the effort. We just try ARM and (with my above patch) otherwise skip the test.

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