[llvm] [Release] Install compiler-rt builtins during Phase 1 on AIX (PR #81485)

[via llvm-commits]

azhan92 wrote:

> > @hubert-reinterpretcast I was trying to copy the logic that was there before, so whatever that was is correct.
> 
> @tstellar, it seems to me that there was special treatment of neither AIX nor Phase 2 in the state prior to [fcae8ce](https://github.com/llvm/llvm-project/commit/fcae8ce77e2256920459fb4cf428a212d6560b68), so (since we do know that special AIX behavior is intended at least for Phase 1) I interpret your statements as there being no broad intent for special Phase 2 behavior.
> 
> @azhan92, can you see if a combination of the corrected install target with a condition to apply only for Phase 1 on AIX works? If not, then also apply for Phase 2 on AIX.

It looks like this statement is necessary for Phase 2 on AIX as well. Should I just remove the `-o $Phase" == "1"` part of the condition then? 

https://github.com/llvm/llvm-project/pull/81485