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

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> @mstorsjo @DavidSpickett can you have a try to use `-print-target-triple` instead of `-print-effective-triple`?

That does seem to do the right thing:
```
$ clang --target=armv7-w64-windows-gnu -print-effective-triple
thumbv7-w64-windows-gnu
$ clang --target=armv7-w64-windows-gnu -print-target-triple
armv7-w64-windows-gnu
$ clang --target=armv7m-none-eabi -print-effective-triple
thumbv7m-none-unknown-eabi
$ clang --target=armv7m-none-eabi -print-target-triple
armv7m-none-unknown-eabi
```

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