[GPU] Shaders to common, xb buildshaders instead of buildhlsl

src/xenia/gpu/shaders/float24_round.ps.hlsl

@@ -0,0 +1,16 @@
+#include "pixel_formats.hlsli"
+#include "xenos_draw.hlsli"
+
+struct XePSInput {
+  XeVertexPrePS pre_ps;
+  sample float4 position : SV_Position;
+};
+
+precise float main(XePSInput xe_input) : SV_Depth {
+  // Input Z may be outside the viewport range (it's clamped after the shader).
+  // Assuming that 0...0.5 on the host corresponds to 0...1 on the guest, to
+  // allow for safe reinterpretation of any 24-bit value to and from float24
+  // depth using depth output without unrestricted depth range.
+  return asfloat(XeFloat20e4To32(
+      XeFloat32To20e4(asuint(saturate(xe_input.position.z * 2.0f))), true));
+}