Fix passing of RIDs in dotnet publish for back-compat

Author: captainsafia

src/Aspire.Hosting/Publishing/ResourceContainerImageBuilder.cs

@@ -272,7 +272,20 @@ private async Task<bool> ExecuteDotnetPublishAsync(IResource resource, Container
 
             if (options.TargetPlatform is not null)
             {
-                arguments += $" /p:RuntimeIdentifiers=\"{options.TargetPlatform.Value.ToMSBuildRuntimeIdentifierString()}\"";
+                // Use the appropriate MSBuild property based on the number of RIDs
+                var runtimeIds = options.TargetPlatform.Value.ToMSBuildRuntimeIdentifierString();
+                var ridArray = runtimeIds.Split(';');
+
+                if (ridArray.Length == 1)
+                {
+                    // Single platform - use ContainerRuntimeIdentifier
+                    arguments += $" /p:ContainerRuntimeIdentifier=\"{ridArray[0]}\"";
+                }
+                else
+                {
+                    // Multiple platforms - use RuntimeIdentifiers
+                    arguments += $" /p:RuntimeIdentifiers=\"{runtimeIds}\"";
+                }
             }
         }