[NFC][libc++][libc++abi][libunwind][test] Fix/unify AIX triples used in LIT tests (#101196)

This patch fixes/unifies AIX target triples used in libc++, libc++abi,
and libunwind LIT tests.

NOKEYCHECK=True
GitOrigin-RevId: 2d3655037ccfa276cb0949c2ce0cff56985f6637
6 files changed