CI: Optionally run distcheck, but without actually running the tests

This can be used to verify that we can build a release tarball using
Autotools, without being subject to known-failing tests (which are less
straightforward to fix). Since commit 44a2d5d6 the Meson build skips
the failing a11y tests, but we don't have an equally easy mechanism
to skip those on Autotools.

Signed-off-by: Simon McVittie <smcv@debian.org>

.gitlab-ci/test-docker-autotools.sh

@@ -16,3 +16,8 @@ cd _build
     --enable-xinerama \
     --enable-gtk-doc
 make -j8
+
+if [ -n "${DO_DISTCHECK-}" ]; then
+  make -j8 check SKIP_GDKTARGET="echo Not actually running tests for now"
+  make -j8 distcheck SKIP_GDKTARGET="echo Not actually running tests for now"
+fi