Set up continuous delivery for Fedora Rawhide/30

This is achieved using "jobs" from packit-as-a-service, more
specifically the propose_downstream job. Furthermore
sync_from_downstream job is configured to keep the spec file
synchronized and prevent merge conflicts for new releases.

Also a small change in Makefile was necessary as it does not reflect the
current state of the spec file in Fedora dist-git (tarball name is
different). The spec file itself is not modified in this commit, because
it will be synchronized automatically using Packit.

Makefile

@@ -1,5 +1,5 @@
 PACKAGE_NAME = osbuild
-VERSION = $$(rpmspec -q --qf '%{version}\n' osbuild.spec | head -1)
+VERSION = $$(python3 setup.py --version)
 
 .PHONY: sdist tarball srpm rpm copy-rpms-to-test check-working-directory vagrant-test vagrant-test-keep-running
 
@@ -10,6 +10,9 @@ sdist:
 tarball:
 	git archive --prefix=osbuild-$(VERSION)/ --format=tar.gz HEAD > $(PACKAGE_NAME)-$(VERSION).tar.gz
 
+tarball-alternative:
+	git archive --prefix=osbuild-$(VERSION)/ --format=tar.gz HEAD > $(VERSION).tar.gz
+
 srpm: $(PACKAGE_NAME).spec tarball
 	/usr/bin/rpmbuild -bs \
 	  --define "_sourcedir $(CURDIR)" \