Fix issue with separable shader validation in iomapper

Test/iomap.blockOutVariableIn.geom

@@ -0,0 +1,28 @@
+#version 440
+
+layout(triangles) in;
+layout(triangle_strip, max_vertices=3) out;
+
+layout(location = 0) in vec4 in_a1[3];
+layout(location = 1) in vec2 in_a2[3];
+
+layout(location = 0) out vec4 a1;
+layout(location = 1) out vec2 a2;
+
+void main()
+{
+    a1 = in_a1[0];
+    a2 = in_a2[0];
+    gl_Position = vec4(1.0);
+    EmitVertex();
+
+    a1 = in_a1[1];
+    a2 = in_a2[1];
+    gl_Position = vec4(1.0);
+    EmitVertex();
+
+    a1 = in_a1[2];
+    a2 = in_a2[2];
+    gl_Position = vec4(1.0);
+    EmitVertex();
+}