[sk] Fix(?) logging for asset creation script subprocess
[sk] Fix(?) logging for asset creation script subprocess

Change-Id: Ie5f42bcc54e7cfc063d83e64e70241ccd295ba17
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/420476
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@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