[clang] [clang][PowerPC] Add flag to enable compatibility with GNU for complex arguments (PR #77732)

[Folkert de Vries via cfe-commits]

folkertdev wrote:

I'm interested in picking this up. Do we really think that this should be configurable though? Mirroring GCC sounds like clearly the right solution, if you need to be compatible with older clang you can just wrap the complex value in a struct.

https://github.com/llvm/llvm-project/pull/77732