Add some tests for no stage inputs or outputs in HLSL.

reference/shaders-hlsl/frag/no-return.frag

@@ -0,0 +1,8 @@
+void frag_main()
+{
+}
+
+void main()
+{
+    frag_main();
+}

reference/shaders-hlsl/frag/no-return2.frag

@@ -0,0 +1,17 @@
+static float4 vColor;
+
+struct SPIRV_Cross_Input
+{
+    float4 vColor : TEXCOORD0;
+};
+
+void frag_main()
+{
+    float4 v = vColor;
+}
+
+void main(SPIRV_Cross_Input stage_input)
+{
+    vColor = stage_input.vColor;
+    frag_main();
+}

reference/shaders-hlsl/vert/no-input.vert

@@ -0,0 +1,18 @@
+static float4 gl_Position;
+struct SPIRV_Cross_Output
+{
+    float4 gl_Position : SV_Position;
+};
+
+void vert_main()
+{
+    gl_Position = float4(1.0f, 1.0f, 1.0f, 1.0f);
+}
+
+SPIRV_Cross_Output main()
+{
+    vert_main();
+    SPIRV_Cross_Output stage_output;
+    stage_output.gl_Position = gl_Position;
+    return stage_output;
+}

shaders-hlsl/frag/no-return.frag

@@ -0,0 +1,5 @@
+#version 310 es
+
+void main()
+{
+}

shaders-hlsl/frag/no-return2.frag

@@ -0,0 +1,9 @@
+#version 310 es
+precision mediump float;
+
+layout(location = 0) in vec4 vColor;
+
+void main()
+{
+	vec4 v = vColor;
+}

shaders-hlsl/vert/no-input.vert

@@ -0,0 +1,6 @@
+#version 310 es
+
+void main()
+{
+	gl_Position = vec4(1.0);
+}