[HDRP] Fixed shadergraph double save (#4916)

* Don't need to save twice shadergraph the first time we create a graph

* Updated changelog

Author: Antoine Lelievre

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

@@ -256,6 +256,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed issue with sky settings being ignored when using the recorder and path tracing (case 1340507).
 - Fixed some resolution aliasing for physically based depth of field (case 1340551).
 - Fixed an issue with resolution dependence for physically based depth of field.
+- Fixed the shader graph files that was still dirty after the first save (case 1342039).
 
 ### Changed
 - Changed Window/Render Pipeline/HD Render Pipeline Wizard to Window/Rendering/HDRP Wizard

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/HDSubTarget.cs

@@ -113,6 +113,7 @@ public override void Setup(ref TargetSetupContext context)
         {
             Migrate();
 
+            systemData.materialNeedsUpdateHash = ComputeMaterialNeedsUpdateHash();
             context.AddAssetDependency(kSourceCodeGuid, AssetCollection.Flags.SourceDependency);
             context.AddAssetDependency(subTargetAssetGuid, AssetCollection.Flags.SourceDependency);
             var inspector = TargetsVFX() ? VFXHDRPSubTarget.Inspector : customInspector;