What changes must I make to the .pro file if I want to execute chmod command, execute the output binary file, or do some other operations.
Another way to make things in given order is to use empty "super" target:
super.depends = target_pre first target_post
QMAKE_EXTRA_TARGETS += super
Where first - is default qmake target, and target_pre and target_post some custom targets. Now make super just do the thing.
EDIT: looks like in last versions of Qt build of dependencies is running in paralell so this solution wouldn't work.