Fix Vulkan unlit single-source HLSL compilation

engine/assets/builtin/shaders/unlit/unlit.shader

@@ -11,19 +11,56 @@ Shader "Builtin Unlit"
         {
             Name "Unlit"
             Tags { "LightMode" = "Unlit" }
-            Resources
-            {
-                PerObjectConstants (ConstantBuffer, 0, 0) [Semantic(PerObject)]
-                MaterialConstants (ConstantBuffer, 1, 0) [Semantic(Material)]
-                BaseColorTexture (Texture2D, 2, 0) [Semantic(BaseColorTexture)]
-                LinearClampSampler (Sampler, 3, 0) [Semantic(LinearClampSampler)]
-            }
+            Cull Back
+            ZWrite On
+            ZTest LEqual
             HLSLPROGRAM
+            #pragma target 4.5
             #pragma vertex MainVS
             #pragma fragment MainPS
-            #pragma backend D3D12 HLSL "unlit.vs.hlsl" "unlit.ps.hlsl" vs_5_0 ps_5_0
-            #pragma backend OpenGL GLSL "unlit.vert.glsl" "unlit.frag.glsl"
-            #pragma backend Vulkan GLSL "unlit.vert.vk.glsl" "unlit.frag.vk.glsl"
+            cbuffer PerObjectConstants : register(b0)
+            {
+                float4x4 gProjectionMatrix;
+                float4x4 gViewMatrix;
+                float4x4 gModelMatrix;
+                float4x4 gNormalMatrix;
+            };
+
+            cbuffer MaterialConstants : register(b1)
+            {
+                float4 gBaseColorFactor;
+            };
+
+            Texture2D BaseColorTexture : register(t0);
+            SamplerState LinearClampSampler : register(s0);
+
+            struct VSInput
+            {
+                float3 position : POSITION;
+                float3 normal : NORMAL;
+                float2 texcoord : TEXCOORD0;
+            };
+
+            struct PSInput
+            {
+                float4 position : SV_POSITION;
+                float2 texcoord : TEXCOORD0;
+            };
+
+            PSInput MainVS(VSInput input)
+            {
+                PSInput output;
+                const float4 positionWS = mul(gModelMatrix, float4(input.position, 1.0f));
+                const float4 positionVS = mul(gViewMatrix, positionWS);
+                output.position = mul(gProjectionMatrix, positionVS);
+                output.texcoord = input.texcoord;
+                return output;
+            }
+
+            float4 MainPS(PSInput input) : SV_TARGET
+            {
+                return BaseColorTexture.Sample(LinearClampSampler, input.texcoord) * gBaseColorFactor;
+            }
             ENDHLSL
         }
     }