[clang] [clang][Itanium Mangle] Enable mangling of enclosing class for member… (PR #110503)

[Utkarsh Saxena via cfe-commits]

https://github.com/usx95 commented:

Thanks. Left a comment about adding a FIXME to remove ABI compat checks and figuring out the support for past ABI.

https://github.com/llvm/llvm-project/pull/110503