[llvm] [flang-rt] replace the triple dir to 'aix' for flang-rt to be consistent with clang on AIX. (PR #130875)

[Michael Kruse via llvm-commits]

Meinersbur wrote:

> Actually, `compiler-rt` build on AIX doesn't call `get_compiler_rt_target`, so it shouldn't be affected.

How so? What is stopping someone to set `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON` on AIX? Is it just not an unsupported configuration?

https://github.com/llvm/llvm-project/pull/130875