[driver] Allow `ld` as a driver alias to lld (#90515)

This adds a "hidden" alias kind that allows using LLD when symlinked as
`ld`; however, it does not install `ld` as a symlink. This is to allow
either using a mixed toolchain with both LLD and GNU ld, or a pure LLD
toolchain where LLD has been installed (or symlinked) to `ld` for
compatibility w/ older tools that expect `ld`.