[clang] [Driver] Add support for GCC installation detection in Baremetal toolchain (PR #121829)

[Peter Smith via cfe-commits]

https://github.com/smithp35 approved this pull request.

I've rechecked the toolchain with the latest change and I can now build with `--target=arm-none-eabi -march=armv7-m`  with a GCC toolchain in `/usr/lib/arm-none-eabi` 

Putting the approve back on.

https://github.com/llvm/llvm-project/pull/121829