Don't set JAVA_HOME on Mac OS X

...for one, it doesn't appear necessary there ("needed for awt"), and for
another setting it according to Oracle's JRE 7 would prevent a subsequent
visit to the Advanced preferences pane from listing Apple's JRE 6, as launching
that java and reading its system properties would be fooled by the JAVA_HOME and
report the Oracle system properties instead.

Change-Id: I02d82de6113b44b3cae3fb55cd83177fe852d769

jvmfwk/plugins/sunmajor/pluginlib/sunjavaplugin.cxx

@@ -595,7 +595,7 @@ javaPluginError jfw_plugin_startJavaVirtualMachine(
          return JFW_PLUGIN_E_VM_CREATION_FAILED;
      }
 
-#ifdef UNX
+#if defined UNX && !defined MACOSX
     //Setting the JAVA_HOME is needed for awt
     OUString javaHome("JAVA_HOME=");
     OUString sPathLocation;