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.
Gold can be enabled by setting the
gold USE flag for sys-devel/binutils. Additionally, setting
default-gold will make ld.gold the default linker.
# enable gold and set it as default sys-devel/binutils gold default-gold
After setting the USE flags, re-install binutils:
emerge --ask --changed-use --deep --oneshot --verbose sys-devel/binutils