The default binutils linker used by gcc, the bfd linker, is slow. The new replacement, gold, has been distributed alongside gcc for several years now, and is a well mature, and much faster, replacement. A new contender, lld, is even faster (but maybe not mature enough).

We will need a new configure argument to be able to select the linker to use. Suggested format: --with-toolchain-linker=[bfd|gold|ldd]. It will only be valid for gcc. Configure should verify that the selected linker in fact is present and runnable.

As a future improvement, gold also allows for incremental linking. Turning on that is outside the scope of this issue.