Fix build

>   /__w/1/s/artifacts/sb/package-cache/microsoft.dotnet.arcade.sdk/9.0.0-beta.24106.2/tools/Workarounds.targets(79,5): error : PackageProjectUrl must be specified [/__w/1/s/artifacts/sb/src/src/Microsoft.DotNet.Arcade.Sdk/Microsoft.DotNet.Arcade.Sdk.csproj]

Author: am11

Directory.Build.props

@@ -13,6 +13,7 @@
     <IsShipping>false</IsShipping>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
+    <RepositoryUrl>https://github.com/dotnet/arcade</RepositoryUrl>
   </PropertyGroup>
 
 </Project>