[msbuild] Allow the remote Build process to run on newer .NET version…

…s than the one it was built for.

This makes it possible to run the build agent when .NET 9 is installed on the
mac.

msbuild/Messaging/Xamarin.Messaging.Build/Xamarin.Messaging.Build.csproj

@@ -11,6 +11,7 @@
     <LangVersion>latest</LangVersion>
     <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <RollForward>LatestMajor</RollForward>
   </PropertyGroup>
 
   <PropertyGroup Label="Messaging">