Add a pkgconfig file and script to fix it up at build time.
Also fix extern "C" for the qcow_utils header.
BUG=chromium:806119
TEST=emerge-eve-kvm crosvm
Change-Id: Ib69d9e88b42d2f2c8661798c37537a4236e0506e
Reviewed-on: https://chromium-review.googlesource.com/891572
Commit-Ready: Stephen Barber <smbarber@chromium.org>
Tested-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
