[clang] [flang] [clang][driver] Special care for linker flags in config files (PR #117573)

[Paul Osmialowski via cfe-commits]

pawosm-arm wrote:

> It's worth spending more time discussing the metacharacter.
> 
> `^` can be interpreted as `^` in regex, which means the beginning. `$`, on the other side, suggests the end. While I agree that `@` for response files is not a good choice, I personally would not rule out `$` just because shell/makefile variable substitution uses it.
> 
> In CCC_OVERRIDE_OPTIONS (clang/lib/Driver/Driver.cpp), `^` is to add an option at the beginning, but there is no `$`. There is `+`, whose meaning is slightly different.

I have no spare time for discussing it, so I turned it to $

https://github.com/llvm/llvm-project/pull/117573