travis: compile with mingw in both production and debug flavours
This should detect anything that is only a build failure when embedded
tests or verbose mode are enabled, such as the missing include fixed
in commit 4858faf. I'm not enabling embedded tests and verbose mode
orthogonally because we don't want CI builds to take too long.
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Ralf Habacker <ralf.habacker@freenet.de>
(cherry picked from commit
8f6fe1451ead14b82475177f40bbc2c256cba876)