[llvm] [PowerPC][NFC] Add base test case for small-local-dynamic-tls on AIX (PR #84711)

[Chen Zheng via llvm-commits]

https://github.com/chenzheng1030 commented:

See https://llvm.org/docs/TestingGuide.html#best-practices-for-regression-tests

I think we should avoid any unnamed instructions in the input IR.

Since the files are too big, could you please simply show how do you arrange these tests?  Thanks a lot.

https://github.com/llvm/llvm-project/pull/84711