Makefile: Build utils for both dynamic and static version.
Makefile: Build utils for both dynamic and static version.

The auto update process (especially firmware updater) needs static vboot
utilitys but normal OS images, including recovery images, don't need
that. We should build both dynamic and static binaries at the same time
for images to choose what they need.

Currently only `crossystem` will build static version. And after this
change is merged:

(cd /build/reef/usr/bin; file crossystem*)
crossystem:   ELF 64-bit LSB shared object
crossystem_s: ELF 64-bit LSB executable

(cd /build/reef/usr/bin; du -sh crossystem*)
40K  crossystem
808K crossystem_s

BUG=chromium:764753,chromium:765499
TEST=emerge-reef vboot_reference
BRANCH=None

Change-Id: Ibd66c87bb44c5593767aeb710240e0165103f016
Reviewed-on: https://chromium-review.googlesource.com/668274
Commit-Ready: Hung-Te Lin <8a7fce4940baad93a69f5073b383c85deed9d9c4@chromium.org>
Tested-by: Hung-Te Lin <8a7fce4940baad93a69f5073b383c85deed9d9c4@chromium.org>
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot