d/rules: Use xvfb-run for the test suite

because the validation of .ui files using gtk-builder-tool
might fail otherwise.

debian/control

@@ -25,6 +25,8 @@ Build-Depends:
  libsoup2.4-dev,
  libsqlite3-dev,
  meson,
+ xauth,
+ xvfb,
 Standards-Version: 4.5.0
 Homepage: https://source.puri.sm/Librem5/chatty
 Vcs-Browser: https://salsa.debian.org/DebianOnMobile-team/chatty

debian/rules

@@ -14,3 +14,8 @@ override_dh_installman:
 	help2man --no-info --name "XMPP and SMS messaging" --section=1 \
 		debian/chatty/usr/bin/chatty > \
 		debian/chatty/usr/share/man/man1/chatty.1
+
+# otherwise the tests running gtk-builder-tool to validate
+# .ui files might fail
+override_dh_auto_test:
+	xvfb-run dh_auto_test