[headless] Do not use libpci with headless.

Headless doesn't use GPU, therefore it doesn't need libpci.

R=alexclarke@chromium.org,skyostil@chromium.org
BUG=546953

Review-Url: https://codereview.chromium.org/1942283003
Cr-Commit-Position: refs/heads/master@{#391298}
1 file changed