[gtk+] Use the cairo renderer for gtk tests for now

[Matthias Clasen <matthiasc src gnome org>]

commit 2f96592e80123d6268e11acecbf00c27c5b7e468
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Oct 18 16:45:52 2017 +0200

    Use the cairo renderer for gtk tests for now
    
    We haven't tracked down yet why the window size tests
    fail with Vulkan, so use cairo for now.

 testsuite/gtk/meson.build |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/testsuite/gtk/meson.build b/testsuite/gtk/meson.build
index dab8a50..2778c63 100644
--- a/testsuite/gtk/meson.build
+++ b/testsuite/gtk/meson.build
@@ -80,6 +80,7 @@ foreach t : tests
               'GSETTINGS_BACKEND=memory',
               'GTK_CSD=1',
               'G_ENABLE_DIAGNOSTIC=0',
+              'GSK_RENDERER=cairo',
               'G_TEST_SRCDIR=@0@'.format(meson.current_source_dir()),
               'G_TEST_BUILDDIR=@0@'.format(meson.current_build_dir())
             ],