While the job is pretty fast for only a few targets we still want to
catch breakage of the build. By splitting the test step we can
allow_failures for that while still ensuring we don't miss the build
breaking.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20201002091538.3017-1-alex.bennee@linaro.org>