gold uses g++ to link which doesn't recognise -all-static. It appears as
if -static should work for both libtool and g++ but for some reason it
doesn't. Remove the restriction that gold can't be included in a static
toolchain. When a static toolchain is requested pass
--with-gold-ldflags=--static to configure. Finally build gold separately
so it does not get the extra_make_flags which may contain -all-static.
Signed-off-by: Chris Packham <judge.packham@gmail.com>