Fix issue with remapping global uniform blocks

Avoid adding global uniform blocks to stages that don't already have it.
Otherwise multiple stages point to the same block object, and a
remapping that occurs later on will change the mapping on multiple
stages.

Test/vk.relaxed.changeSet.vert

@@ -0,0 +1,16 @@
+#version 460
+
+in vec2 aPos;
+in vec2 aUV;
+in vec4 aColor;
+uniform mat4 projectionMatrix;
+
+out vec4 Color;
+out vec2 UV;
+
+void main()
+{
+    Color = aColor;
+    UV = aUV;
+    gl_Position = projectionMatrix * vec4(aPos, 0, 1);
+}