Bring back skip_build option

[MartinBasti]

This option must be kept for BW compatibility, tools like rpkg are adding skip_build=False to task options.

However when skip_build is True, build must fail becasue this feature has been dropped

CLOUDBLD-10709

Signed-off-by: Martin Basti mbasti@redhat.com

Maintainers will complete the following section

• [x] Commit messages are descriptive enough
• [x] Code coverage from testing does not decrease and new code is covered
• [x] JSON/YAML configuration changes are updated in the relevant schema
• n/a Pull request has a link to an osbs-docs PR for user documentation updates

[MartinBasti]

release notes:

• 'skip_build' option is deprecated, builder doesn't allow to skip builds anymore (it was part of deprecated OSBS autorebuild feature)