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

[YunQiang Su via llvm-commits]

wzssyqa wrote:

There still some problem for `armv7m-none-eabi`:
1. `clang --target=armv7m-none-eabi -print-target-triple` out put
```
armv7m-none-unknown-eabi
```
Is it correct? Should we fix the C++ code to normalize triples?

2. in `livcxx/utils/ci/run-buildbot`, `install/lib/armv7m-none-eabi` is hardcoded.
    should we use `clang -print-target-triple` for it?

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