Sign and harden pkgs (#47996)

Author: mmitche

eng/Signing.props

@@ -55,6 +55,10 @@
     <FileSignInfo Include="Nerdbank.Streams.dll" CertificateName="$(ExternalCertificateId)" />
     <FileSignInfo Include="Newtonsoft.Json.dll" CertificateName="$(ExternalCertificateId)" />
     <FileSignInfo Include="Valleysoft.DockerCredsProvider.dll" CertificateName="$(ExternalCertificateId)" />
+
+    <!-- Additionally, we need to notarize any .pkg files -->
+    <MacOSPkg Include="$(ArtifactsShippingPackagesDir)**/dotnet-sdk*.pkg" Exclude="$(ArtifactsShippingPackagesDir)**/dotnet-sdk-internal*.pkg" />
+    <FileSignInfo Include="@(MacOSPkg->'%(Filename)%(Extension)')" CertificateName="MacDeveloperWithNotarization" />
   </ItemGroup>
 
   <ItemGroup>