vkgears is silently disabled without Wayland

$ meson setup --auto-features=disabled -Dx11=enabled -Dvulkan=enabled /tmp/demos_build
$ meson compile -C /tmp/demos_build
$ ls -l /tmp/demos_build/src/vulkan
total 0

Workaround:

diff --git a/meson.build b/meson.build
index f93a731d..bac71e0c 100644
--- a/meson.build
+++ b/meson.build
@@ -60,7 +60,6 @@ dep_xcb = dependency('xcb, xkbcommon, xkbcommon-x11',
 )
 dep_wayland = dependency('wayland-client, wayland-egl, xkbcommon',
   required : get_option('wayland'),
-  disabler : true
 )
 
 if dep_wayland.found()