Added SourceRoot build property.

reduckted · reduckted · commit 7872556d563a · 2022-04-22T22:26:12.000+10:00
dotnet/roslyn#37379 (comment)
diff --git a/Directory.Build.props b/Directory.Build.props
@@ -8,4 +8,8 @@
     <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
   </PropertyGroup>
 
+  <ItemGroup>
+    <SourceRoot Include="$(MSBuildThisFileDirectory)/"/>
+  </ItemGroup>
+
 </Project>
