rhi: multiview manual test: exercise passing through gl_ViewIndex

Change-Id: Iee9a29250061ca57ea30e3e545d1a6de952c1852
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

tests/manual/rhi/multiview/multiview.frag

@@ -1,10 +1,11 @@
 #version 440
 
 layout(location = 0) in vec3 v_color;
+layout(location = 1) in flat uint v_viewIndex;
 
 layout(location = 0) out vec4 fragColor;
 
 void main()
 {
-    fragColor = vec4(v_color, 1.0);
+    fragColor = vec4(v_color + v_viewIndex * 0.5, 1.0);
 }

tests/manual/rhi/multiview/multiview.vert

@@ -6,6 +6,7 @@ layout(location = 1) in vec3 color;
 layout(location = 2) in vec3 translation;
 
 layout(location = 0) out vec3 v_color;
+layout(location = 1) out flat uint v_viewIndex;
 
 layout(std140, binding = 0) uniform buf
 {
@@ -16,4 +17,5 @@ void main()
 {
     v_color = color;
     gl_Position = mvp[gl_ViewIndex] * (pos + vec4(translation, 0.0));
+    v_viewIndex = gl_ViewIndex;
 }