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

[Daniel Chen via cfe-commits]

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@@ -935,6 +935,14 @@ ToolChain::getTargetSubDirPath(StringRef BaseDir) const {
   if (auto Path = getPathForTriple(T))
     return *Path;
 
+  // On AIX, the environment component is not used in the target sub dir name.
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DanielCChen wrote:

I think it is correct that the `-unknown` is NOT stripped. I built `flang-rt` with `-DLLVM_DEFAULT_TARGET_TRIPLE=powerpc64-ibm-aix-unknown \`, `libflang_rt.runtime.a` is published to 
`./lib/clang/21/lib/powerpc64-ibm-aix-unknown/libflang_rt.runtime.a`. which is expected. 
The test cases should be changed to remove the `-unknown` part of add a separate dir for that specific testing.

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