[clang] [clang][AIX] Handle triple environment component for per target runtime directory (PR #140850)

[Daniel Chen via cfe-commits]

DanielCChen wrote:

> > A more general question: It seems neither `compile-rt` nor `flang-rt` uses `getTargetSubDirPath`, so we didn't need to strip to the "base" triple. Sanitizer uses it apparently. Is it by design? @daltenty
> 
> I doubt it, this code is extremely messy and there's duplication everywhere, so I suspect that diverged unintentionally

Yeah, I think I figured it out. I updated my inline comments to suggest a change.

It seems `getTargetSubDirPath` appends the triple dir to the argument. `getRuntimePath` calls `getTargetSubDirPath` with the argument of `resource-dir`/`lib`. Others pass different argument. For example, `getStdlibIncludePath` calls `getTargetSubDirPath`  with `..../include`. 


https://github.com/llvm/llvm-project/pull/140850