A GitLab update will be applied on May 9th, between 8am and 10am, EDT (UTC-04:00). This site may have intermittent delays during that time.
In commit da5ac4bb (cpack: Add `CPACK_INSTALL_CMAKE_CONFIGURATIONS` variable, 2019-07-10, v3.16.0-rc1~165^2) we added support for running the `cpack -C ...` command-line with multiple configurations. Add an explicit test for this. Fixes: #19918