catalyst: update GCC dependencies before building stage1

When bootstrapping a SDK we need to update GCC dependencies to ensure
the GCC built for stage1 is linked against the same library versions as
those that are included in the stage1. Without this updating the mpc
library just results in a broken stage1.

build_library/catalyst.sh

@@ -99,6 +99,7 @@ cat <<EOF
 target: stage1
 # stage1 packages aren't published, save in tmp
 pkgcache_path: ${TEMPDIR}/stage1-${ARCH}-packages
+update_seed: yes
 EOF
 catalyst_stage_default
 }