fix a couple issues with Microsoft.XmlSerailizer.Generator (#73550)

* fix a couple issues with Microsoft.XmlSerailizer.Generator

* update per PR feedback

* update 2 - change default to True

* correct a mistake

Author: HongGit

src/libraries/Microsoft.XmlSerializer.Generator/src/GenerateNupkgProps.targets

@@ -19,6 +19,12 @@
   <ItemGroup>
     <DotNetCliToolReference Include="$(PackageId)" Version="$(PackageVersion)" />
   </ItemGroup>
+  <PropertyGroup>
+    <SgenPackSerializer Condition="'%24(SgenPackSerializer)'==''">True</SgenPackSerializer>
+  </PropertyGroup>
+  <ItemGroup Condition="'%24(SgenPackSerializer)'=='True'">
+    <BuildOutputInPackage Include="%24(OutputPath)%24(AssemblyName).XmlSerializers.dll" />
+  </ItemGroup>
 </Project>
       </PropsFileContents>
     </PropertyGroup>

src/libraries/Microsoft.XmlSerializer.Generator/src/build/Microsoft.XmlSerializer.Generator.targets

@@ -43,7 +43,7 @@
       Encoding="Unicode"/>      
   </Target> 
 
-  <Target Name="GenerateSerializationAssembly" AfterTargets="Build">
+  <Target Name="GenerateSerializationAssembly" AfterTargets="Build" Inputs="@(ReferencePath);@(IntermediateAssembly)" Outputs="$(_SerializerDllIntermediateFolder)">
     <Delete Condition="Exists('$(_SerializerDllIntermediateFolder)') == 'true'" Files="$(_SerializerDllIntermediateFolder)" ContinueOnError="true"/>
     <Delete Condition="Exists('$(_SerializerPdbIntermediateFolder)') == 'true'" Files="$(_SerializerPdbIntermediateFolder)" ContinueOnError="true"/>
     <Delete Condition="Exists('$(_SerializerCsIntermediateFolder)') == 'true'"  Files="$(_SerializerCsIntermediateFolder)" ContinueOnError="true"/>