add 32/64 bit preference on OS X, tweak library errors for bit depths

app/src/processing/mode/java/JavaBuild.java

@@ -1095,6 +1095,23 @@ public class JavaBuild {
   private boolean exportApplication(File destFolder,
                                    int exportPlatform,
                                    int exportBits) throws IOException, SketchException {
+    // TODO this should probably be a dialog box instead of a warning  
+    // on the terminal. And the message should be written better than this.
+    // http://code.google.com/p/processing/issues/detail?id=884
+    for (Library library : importedLibraries) {
+      if (!library.supportsArch(exportPlatform, exportBits)) {
+        String pn = PConstants.platformNames[exportPlatform];
+        System.err.println("The application." + pn + exportBits + 
+                           " folder will not be created because no " +  
+                           exportBits + "-bit version of " +
+                           library.getName() + 
+                           " is available for " + pn);
+        return true;  // don't cancel export for this, just move along
+      }
+    }
+
+    /// prep the output directory
+
     mode.prepareExportFolder(destFolder);