[clang] [compiler-rt] [llvm] [AIX] Implement the ifunc attribute. (PR #153049)

[Wael Yehia via cfe-commits]

w2yehia wrote:

@tbaederr I'm not able to reproduce this the short way, so I'm disabling it (commit `13c9276daa86`) on your buildbot by adding `REQUIRES: asserts` for now.

https://github.com/llvm/llvm-project/pull/153049