Rather than having a toolchain package we use for the cross-compilers and
installing a different one for the target build dir, use the same package.
This makes updating more logical as we only have to do it in one place.
BUG=chromium-os:24928
TEST=`cbuildbot amd64-generic-full` works
TEST=`cbuildbot arm-generic-full` works
TEST=`cbuildbot x86-generic-full` works
TEST=build_packages+build_image for x86-alex boots & works
Change-Id: Ib083c3d2eae75d6f5437203990599cdc837dd9dc
Reviewed-on: https://gerrit.chromium.org/gerrit/24722
Reviewed-by: Anush Elangovan <anush@google.com>
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
