in general, SOLARIS should use /usr/bin/ld.

Make equivalent to unxgcc.mk (with gld).
NB: use $(READELF) updated in configure.ac and config_host.mk.in

Change-Id: Iaf175fb7db095c567e9837eac8456c0c3809e334
Signed-off-by: Michael Stahl <mstahl@redhat.com>