Make sure that variables which are (or may be) used

in an ".opt" file are defined to some value (even
if it is empty). Without this, a test suite run
aborted on Windows for "embedded".

This fix was applied dusing the build of 5.4.2-beta.

mysql-test/mysql-test-run.pl

@@ -1781,6 +1781,14 @@ sub environment_setup {
     $ENV{'HA_EXAMPLE_SO'}="'".$plugin_filename."'";
     $ENV{'EXAMPLE_PLUGIN_LOAD'}="--plugin_load=;EXAMPLE=".$plugin_filename.";";
   }
+  else
+  {
+    # Some ".opt" files use some of these variables, so they must be defined
+    $ENV{'EXAMPLE_PLUGIN'}= "";
+    $ENV{'EXAMPLE_PLUGIN_OPT'}= "";
+    $ENV{'HA_EXAMPLE_SO'}= "";
+    $ENV{'EXAMPLE_PLUGIN_LOAD'}= "";
+  }
 
   # ----------------------------------------------------
   # Add the path where mysqld will find mypluglib.so