Avoid error from no rspec results

If no rspec tests are configured at all then there is no rspec.xml generated to be uploaded as an artifact.

This results in a harmless but confusing message in the job log:

Uploading artifacts for successful job
Uploading artifacts...
WARNING: code/rspec.xml: no matching files

touch the file always so it can always be uploaded.

Looks like when this is uploaded to gitlab it just displays that the rspec results are null which is just fine.