Gold

gold is a new linker intended as a replacement for the ld.bfd linker.

The two installed linkers are available directly as ld.bfd and ld.gold respectively. Additionally, the default linker is also installed as ld -- and this binary is used by compilers.

Warning
When I built grub2 after following these steps, my system became unbootable. Proceed with caution.

The easy way
Emerge >=sys-devel/binutils-config-3 and set default linker to gold:

The hard way (manually)
The default linker can be changed immediately by linking ld to ld.gold in the binutils directory.

Hard link:

Symbolic link:

To make the change persistent across re-installations of binutils, one should pass a flag to the binutils configure script. This can be done using the EXTRA_ECONF variable in a package.env configuration.