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

[David Spickett via llvm-commits]

DavidSpickett wrote:

`-print-effective-triple` gives:
```
$ /home/david.spickett/build-llvm-aarch64/bin/clang --target=armv7m-none-eabi -print-target-triple
armv7m-none-unknown-eabi
```
Which is more normal, however I still get:
```
-- Installing: /home/david.spickett/llvm-project/build/armv7m-picolibc/install/lib/armv7m-none-unknown-eabi/libclang_rt.builtins.a
+ mv '/home/david.spickett/llvm-project/build/armv7m-picolibc/install/lib/armv7m-none-eabi/*' /home/david.spickett/llvm-project/build/armv7m-picolibc/install/lib
mv: cannot stat '/home/david.spickett/llvm-project/build/armv7m-picolibc/install/lib/armv7m-none-eabi/*': No such file or directory
```
That subdir doesn't exist but the one clang printed does:
```
$ ls /home/david.spickett/llvm-project/build/armv7m-picolibc/install/lib/
armv7m-none-unknown-eabi  crt0-minimal.o   crt0.o  libcrt0-hosted.a   libcrt0-semihost.a  libdummyhost.a  libm.a         picolibc.ld
crt0-hosted.o             crt0-semihost.o  libc.a  libcrt0-minimal.a  libcrt0.a           libg.a          libsemihost.a  picolibcpp.ld
david.spickett at tcwg-jade-03-dev:~/llvm-project$ ls /home/david.spickett/llvm-project/build/armv7m-picolibc/install/lib/armv7m-none-unknown-eabi/
libclang_rt.builtins.a
```
Maybe something in the install step also needs to be updated?

Also it is a bit weird that this is adding a PER_TARGET_RUNTIME_DIR style folder path, in a build that doesn't enable that setting. But I don't have the full context so I'm not sure that's wrong necessarily.

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