Update linux sysroot image

This adds libffi-dev and libdrm-dev to the image
which were recently added with:
https://codereview.chromium.org/1464123002

R=thestig@chromium.org
BUG=559062

Review URL: https://codereview.chromium.org/1466383002

Cr-Commit-Position: refs/heads/master@{#361129}
1 file changed