Make sure that exec runs even if you don't specify an OS

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@270687 13f79535-47bb-0310-9956-ffa450edef68

proposal/myrmidon/src/java/org/apache/antlib/nativelib/Exec.java

@@ -10,11 +10,11 @@ package org.apache.antlib.nativelib;
 import java.io.File;
 import java.io.IOException;
 import java.util.Properties;
+import org.apache.aut.nativelib.Os;
 import org.apache.avalon.excalibur.i18n.ResourceManager;
 import org.apache.avalon.excalibur.i18n.Resources;
 import org.apache.myrmidon.api.AbstractTask;
 import org.apache.myrmidon.api.TaskException;
-import org.apache.aut.nativelib.Os;
 import org.apache.tools.ant.taskdefs.exec.Execute2;
 import org.apache.tools.ant.types.Argument;
 import org.apache.tools.ant.types.Commandline;
@@ -107,7 +107,7 @@ public class Exec
         throws TaskException
     {
         validate();
-        if( Os.isFamily( m_os ) )
+        if( null == m_os || Os.isFamily( m_os ) )
         {
             final Execute2 exe = createExecute();
             doExecute( exe );