sudo mv /usr/bin/ld /usr/bin/ld.orig
sudo install this/repo/Darwin/3.9/ld /usr/bin/ld
# No additional actions required.. it usually just works
install this/repo/FreeBSD/3.9/ld.lld /usr/bin/ld.lld
# Pass -fuse-ld=lld to your compiler f.i. via CFLAGS/CXXFLAGS