[compiler-rt] [libcxx] CompilerRT: Normalize COMPILER_RT_DEFAULT_TARGET_TRIPLE (PR #89234)

[YunQiang Su via llvm-commits]

wzssyqa wrote:

I don't think that this PR changes the clang behavior where to search for libclang_rt.builtins.
Before this patch, clang search libclang_rt.builtins from a `normalized` triple subdir.

I think that your problem is about how `aarch64-none-elf` is normalized.
In current code, `aarch64-none-elf` is normalized to `aarch64-unknown-none-elf`.
If it is incorrect, we can have any PR to it.
See `std::string Triple::normalize(StringRef Str)` in `llvm/lib/TargetParser/Triple.cpp`.

https://github.com/llvm/llvm-project/pull/89234