Fix hair shader compilation issue with Debug Display mode (#2023)

* Fix compilation issue with debug mode and hair

* Update CHANGELOG.md

Author: sebastienlagarde

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -97,6 +97,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed alignment of framesettings in HDRP Default Settings
 - Fixed an exception thrown when closing the look dev because there is no active SRP anymore.
 - Fixed an issue where entering playmode would close the LookDev window.
+- Fixed shader compilation issue with Hair shader and debug display mode
 
 ### Changed
 - Preparation pass for RTSSShadows to be supported by render graph.

com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/Deferred.compute

@@ -176,12 +176,14 @@ void SHADE_OPAQUE_ENTRY(uint3 dispatchThreadId : SV_DispatchThreadID, uint2 grou
     diffuseLighting *= GetCurrentExposureMultiplier();
     specularLighting *= GetCurrentExposureMultiplier();
 
+#ifdef OUTPUT_SPLIT_LIGHTING
     if (_EnableSubsurfaceScattering != 0 && ShouldOutputSplitLighting(bsdfData))
     {
         specularLightingUAV[COORD_TEXTURE2D_X(pixelCoord)] = float4(specularLighting, 1.0);
         diffuseLightingUAV[COORD_TEXTURE2D_X(pixelCoord)]  = TagLightingForSSS(diffuseLighting);
     }
     else
+#endif
     {
         specularLightingUAV[COORD_TEXTURE2D_X(pixelCoord)] = float4(diffuseLighting + specularLighting, 1.0);
     }

com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/LightLoop.hlsl

@@ -163,10 +163,12 @@ void ApplyDebug(LightLoopContext context, PositionInputs posInput, BSDFData bsdf
 
         lightLoopOutput.diffuseLighting = SAMPLE_TEXTURE2D_LOD(_DebugMatCapTexture, s_linear_repeat_sampler, UV, 0).rgb * (_MatcapMixAlbedo > 0  ? defaultColor.rgb * _MatcapViewScale : 1.0f);
 
-        if (ShouldOutputSplitLighting(bsdfData) && _EnableSubsurfaceScattering != 0)
+    #ifdef OUTPUT_SPLIT_LIGHTING
+        if (_EnableSubsurfaceScattering != 0 && ShouldOutputSplitLighting(bsdfData))
         {
             lightLoopOutput.specularLighting = lightLoopOutput.diffuseLighting;
         }
+    #endif
 
     }
 #endif