[metrics] use libchromeos.pc

BUG=chromium-os:24959
TEST=build

Signed-off-by: Elly Jones <ellyjones@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/14012


Reviewed-by: Mike Frysinger <vapier@chromium.org>
(cherry picked from commit 0ea8151d4628ccf500da82206384b8b492a95a0b)

Change-Id: I0c51d49cc7182a19b16d3cb123c43e29be890cbe
Reviewed-on: https://gerrit.chromium.org/gerrit/14505


Reviewed-by: Kees Cook <keescook@chromium.org>
Commit-Ready: Elly Jones <ellyjones@chromium.org>
Tested-by: Elly Jones <ellyjones@chromium.org>