[clang] [llvm] [clang] Add "debug_transparent" attribute (PR #109490)

[Augusto Noronha via cfe-commits]

augusto2112 wrote:

@dwblaikie @AaronBallman this is the "debug_transparent" patch that I opened last year but didn't get around to finish implementing (https://reviews.llvm.org/D146595).

The current version addresses the comments left in the phabricator review:
- Changed the name from debug_trampoline to debug_transparent
- Emits a warning if the attribute is used when emitting debug info that is not DWARF.

https://github.com/llvm/llvm-project/pull/109490