Make 3D cursor work for Vulkan

Shaders/painter/cursor.frag.glsl

@@ -1,5 +1,8 @@
 #version 330
 uniform vec3 tint;
+#ifdef SPIRV
+uniform sampler2D gbufferD; // vulkan unit align
+#endif
 uniform sampler2D tex;
 in vec2 texCoord;
 out vec4 FragColor;