Fixing the “can’t start the AWT” bug for Tomcat6

After a Java upgrade on the OSX, Tomcat6 is not starting properly. The log shows a Java error:

2013-06-27 14:45:40.300 jsvc[57146:203] Apple AWT Java VM was loaded on first thread -- can't start AWT.
Jun 27, 2013 2:45:40 PM org.apache.catalina.startup.Bootstrap initClassLoaders
SEVERE: Class loader creation threw exception
java.lang.InternalError: Can't start the AWT because Java was started on the first thread.  Make sure StartOnFirstThread is not specified in your application's Info.plist ...

To have it properly start through tomcatctl, you need to add the awt.headless option to JAVA_OPTS. This can be done, by modifying the /opt/local/share/java/tomcat6/conf/setenv.local file, and appending this line to it:

export JAVA_OPTS="$JAVA_OPTS -Djava.awt.headless=true"