[PowerPC][AIX] Enable Shrinkwrapping on 32 and 64 bit AIX.

Summary:
Currently Shrinkwrap is not enabled on AIX.
This patch enables shrink wrap on 32 and 64 bit AIX, and 64 bit ELF.

Reviewed By: sfertile, nemanjai

Differential Revision: https://reviews.llvm.org/D95094