[PTFM-7351] Always ignore ./.git when building --remote
Compute the "+git.abcdef" suffix and send it to remote builder.

This preserves autonumbering behavior when the .git directory is not
uploaded to the remote worker.
Fix autonumbering behavior with --remote --no-update.
Merge pull request #26 from dnanexus/PTFM-7351

[PTFM-7351] Always ignore ./.git when building --remote