[Autoroller] Fix Dockerfile
[Autoroller] Fix Dockerfile

Without this I see-
"""
The following packages have unmet dependencies:
 build-essential : Depends: gcc (>= 4:9.2) but it is not going to be installed
                   Depends: g++ (>= 4:9.2) but it is not going to be installed
"""

Change-Id: Ic423ea8c7522a9247d2a6711e94cb8160acbf75a
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/300904
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot