[gtk] ci/msys2: force disable vulkan

[Christoph Reiter <creiter src gnome org>]

commit e610c02a9eada5f2e1e7ddf2dc307dc82d22e256
Author: Christoph Reiter <creiter src gnome org>
Date:   Sat May 26 14:23:58 2018 +0200

    ci/msys2: force disable vulkan
    
    A recent dependency change in MSYS2 made it pull in vulkan, which made
    meson think it's available but it somehow links against the system vulkan dll
    instead.
    
    Disable vulkan for now.

 .gitlab-ci/test-msys2.sh | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci/test-msys2.sh b/.gitlab-ci/test-msys2.sh
index aacc88d048..3abaf9d083 100644
--- a/.gitlab-ci/test-msys2.sh
+++ b/.gitlab-ci/test-msys2.sh
@@ -45,6 +45,7 @@ meson \
     -Denable-x11-backend=false \
     -Denable-wayland-backend=false \
     -Denable-win32-backend=true \
+    -Dvulkan=no \
     _build
 unset CCACHE_DISABLE