[clang] [llvm] [RFC][LLVM][Clang] Add LLVM plugin hook for back-ends (PR #170846)

[Vassil Vassilev via llvm-commits]

https://github.com/vgvassilev commented:

That looks like a reasonable direction to me. Any chance for a test?

https://github.com/llvm/llvm-project/pull/170846