[dist:build] swap copy_dist and uglify tasks

it's more safe to first copy files over and then run the uglify task.
This prevents problems with JavaScript files copied in a copy:dist_* task,
although they should have been copied during copy:build_*. Since in such
a case (destinations are not unique) it's most likely, the result of the
uglify task should "win the race", uglify task will be run last.