Add debugging to fiddler-backend Docker creation

Failing mysteriously https://louhi.dev/6316342352543744/execution-detail/4814501665177600

Step #1: ./create_docker_image.sh: 1: Bad substitution
Step #1: unable to prepare context: unable to evaluate symlinks in Dockerfile path: lstat /infra: no such file or directory
Finished Step #1

Change-Id: I5d1f45eae7095463338d36ea84e9598ea67e1f4a
Bug: b/361559681
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/897296
Auto-Submit: Kaylee Lubick <kjlubick@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
1 file changed