3892359 changed builder args to always be arrays, so concatenation of
rpmbuild options with other strings then failed.
File "/usr/lib/python2.7/site-packages/tito/release/main.py", line 530, in _koji_release
builder.srpm(dist=disttag)
File "/usr/lib/python2.7/site-packages/tito/builder/main.py", line 210, in srpm
rpmbuild_options = self.rpmbuild_options + self._scl_to_rpmbuild_option()
TypeError: can only concatenate list (not "str") to list
Change builder args to be joined by a single space, allowing multiple
arguments to be passed in.