Ensure the existence of etc/{group,passwd} under /usr/local in dev_install

These files are necessary for package installation to work correctly.
When dev_install runs on a base image, there won't be anything under
/usr/local, so we need to ensure that we put the appropriate symlinks
there. We already do this when making a dev or test image, in build_image.

BUG=chromium:205164
TEST=a canary tryjob

Change-Id: I7cdb74440af8f4b3abd3f966dd85ef2a2e43c436
Reviewed-on: https://chromium-review.googlesource.com/183930
Reviewed-by: Chris Masone <cmasone@chromium.org>
Commit-Queue: Chris Masone <cmasone@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>
1 file changed