update of MERGE_NAME macro [Skip CI]

com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl

@@ -38,7 +38,7 @@
 // However, FXC does not support the proper pattern (the one bellow), so we only override it in the case of ray tracing subshaders for the moment.
 // Note that this should be used for all shaders when DX12 used DXC for vert/frag shaders (which it does not for the moment)
 #undef MERGE_NAME
-#define MERGE_NAME_CONCAT(Name, ...) Name ## __VA_ARGS__
+#define MERGE_NAME_CONCAT(Name, X) Name##X
 #define MERGE_NAME(X, Y) MERGE_NAME_CONCAT(X, Y)
 
 #define RAY_TRACING_OPTIONAL_PARAMETERS , IntersectionVertex intersectionVertex, RayCone rayCone, out bool alphaTestResult