Port to FreeBSD PowerPC 64-bit
FreeBSD on PowerPC 64-bit follows the ELF v1 ABI. This was enabled only on Linux so far. We enable ELF-ABIs for all PowerPC by default because most systems follow an ELF-ABI on PowerPC. Exceptions are AIX, for which we have code in place, and OS X, which is no longer supported on PowerPC.
Fixes #15916 (closed).