Add proper MSBuild error (XA4238) for JCW XML import failures

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>

Author: Copilot

src/Xamarin.Android.Build.Tasks/Properties/Resources.Designer.cs

@@ -974,6 +974,12 @@ To use a custom JDK path for a command line build, set the 'JavaSdkDirectory' MS
 {0} - Maven artifact id
 {1} - The HttpClient reported download exception message
 </comment>
+  </data>
+  <data name="XA4238" xml:space="preserve">
+    <value>Could not load Java callable wrapper XML file '{0}': {1}</value>
+    <comment>The following are literal names and should not be translated: Java callable wrapper, XML.
+{0} - Path to XML file
+{1} - Exception message</comment>
   </data>
   <data name="XA4239" xml:space="preserve">
     <value>Unknown Maven repository: '{0}'.</value>

src/Xamarin.Android.Build.Tasks/Properties/Resources.resx

@@ -69,7 +69,13 @@ void GenerateWrappers (List<ITaskItem> assemblies)
 				return;
 			}
 
-			var xml = JavaObjectsXmlFile.Import (wrappersPath, JavaObjectsXmlFileReadType.JavaCallableWrappers);
+			JavaObjectsXmlFile xml;
+			try {
+				xml = JavaObjectsXmlFile.Import (wrappersPath, JavaObjectsXmlFileReadType.JavaCallableWrappers);
+			} catch (InvalidOperationException ex) {
+				Log.LogCodedError ("XA4238", Properties.Resources.XA4238, wrappersPath, ex.Message);
+				return;
+			}
 
 			if (xml.JavaCallableWrappers.Count == 0) {
 				Log.LogDebugMessage ($"'{wrappersPath}' is empty, skipping.");