build: do not run xwayland test for distcheck

The Xwayland test has been broken ever since the migration to the
stand-alone Xwayland server binary.

Disable the test, so 'make distcheck' can actually run.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Boyan Ding <stu_dby@126.com>

Makefile.am

@@ -8,7 +8,8 @@ module_LTLIBRARIES =
 noinst_LTLIBRARIES =
 BUILT_SOURCES =
 
-AM_DISTCHECK_CONFIGURE_FLAGS = --disable-setuid-install
+# Do not run xwayland test while it is known broken.
+AM_DISTCHECK_CONFIGURE_FLAGS = --disable-setuid-install --disable-xwayland-test
 
 EXTRA_DIST = weston.ini.in