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

[Sam James via cfe-commits]

thesamesam wrote:

I took a look and I think it may be too awkward to do, as we'd want to run e.g. readelf afterwards. But an example is `lld/test/ELF/as-needed-not-in-regular.s`. The idea being: if `-Wl,--as-needed` is in the config file, do we correctly prune an unnecessary library from a built object, or is the order wrong? We can check that with `llvm-readelf`.

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