* Update README for gitlab migration
* Update configure.ac bug URL for gitlab migration
* gitlab CI: add a basic build test
* gitlab CI: stop requiring Signed-off-by in commits
* Variable scope reductions as recommended by cppcheck
* gitlab CI: explictly list GNU make to be installed in build environment
OBS-URL: https://build.opensuse.org/package/show/X11:XOrg/xkill?expand=0&rev=9
