[cashew] Use libchrome.pc

Also, add myself to OWNERS, as cashew has no OWNERS and vlaviano is former.

BUG=chromium-os:24959,chromium-os:22007
TEST=Build

Change-Id: Ifec247a85a61829e630b966d74f076a28dca0966
Signed-off-by: Elly Jones <ellyjones@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/14814
Reviewed-by: Kees Cook <keescook@chromium.org>