[compiler-rt] CompilerRT: Normalize COMPILER_RT_DEFAULT_TARGET_TRIPLE (PR #88835)

[David Spickett via llvm-commits]

DavidSpickett wrote:

If you add the libcxx build script changes to that PR it should be run by the libcxx CI so we can confirm that that works too.

https://github.com/llvm/llvm-project/pull/88835