Config option to copy over the extjs-build dir

[nene]

From Sencha Forum:

My only issue is the extjs-build directory in the output dir. It gets blown away every time docs are regenerated. Is there a way to specify a path in the jsduck.config instead of putting the extjs-build directory in there?

There really should be a config option to achieve that, not having to resort into copying it over manually.