respect LDFLAGS settings

Libraries go into $LDLIBS while linker flags go into $LDFLAGS.

Also make sure the utility subdir respects the env $LDFLAGS so that
we can do things like `make LDFLAGS=-static` and get static binaries.

BUG=None
TEST=`emerge vboot_reference` still works
TEST=`emerge-arm-generic vboot_reference` still works

Change-Id: I989a21bc559bc6d471bc33c057c708bda2eda67e
Reviewed-on: https://gerrit.chromium.org/gerrit/24728
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
2 files changed