Extract the crossbuild job templates to a new file
(crossbuild-template.yml) to be able to reuse them
without having to run all the jobs included, which
are mainly useful for mainstream CI.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Message-Id: <20210519185504.2198573-5-f4bug@amsat.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>