[D3D12] Add HLSL building to xenia-build

src/xenia/ui/d3d12/shaders/immediate.vs.hlsl

@@ -0,0 +1,21 @@
+float2 scale : register(b0);
+
+struct vs_input {
+  float2 pos : POSITION;
+  float2 uv : TEXCOORD;
+  float4 color : COLOR;
+};
+
+struct vs_output {
+  float4 pos : SV_Position;
+  float2 uv : TEXCOORD0;
+  float4 color : TEXCOORD1;
+};
+
+vs_output main(vs_input input) {
+  vs_output output;
+  output.pos = float4(scale * input.pos, 0.0, 1.0);
+  output.uv = input.uv;
+  output.color = input.color;
+  return output;
+}