[generator] Add run configuration in csproj to run/debug the maccatalyst version. (#17124)

src/bgen/bgen.csproj

@@ -124,6 +124,16 @@
       <Variable name="XamarinMacFrameworkRoot" value="../../_mac-build/Library/Frameworks/Xamarin.Mac.framework/Versions/Current" />
     </EnvironmentVariables>
   </PropertyGroup>
+  <PropertyGroup Condition=" '$(RunConfiguration)' == 'maccatalyst' ">
+    <StartAction>Project</StartAction>
+    <StartArguments>@build/dotnet/$(RunConfiguration)/$(RunConfiguration).rsp</StartArguments>
+    <StartWorkingDirectory>..</StartWorkingDirectory>
+    <ExternalConsole>false</ExternalConsole>
+    <EnvironmentVariables>
+      <Variable name="MD_MTOUCH_SDK_ROOT" value="../../_ios-build//Library/Frameworks/Xamarin.iOS.framework/Versions/git" />
+      <Variable name="XamarinMacFrameworkRoot" value="../../_mac-build/Library/Frameworks/Xamarin.Mac.framework/Versions/Current" />
+    </EnvironmentVariables>
+  </PropertyGroup>
 
   <Target Name="AfterBuild">
     <Exec Command="make bgen dotnet -C .. -j" />