On my system (Nix), the compiler produces a `-dynamic-linker=/nix/store/...` in
the linker call scanned by get_padded_dynamic_linker_option.
But the regex can't deal with the `=` there, it requires a ` `. Fix that.
We also do the same in configure.py, and remove the Nix-specific hack
which used to disable the entire mechanism.
Closesscylladb/scylladb#22308