Today if a user makes a mistake in DynamicConstants and introduces a coding style error, this error will not be spotted on the first run of the precommit target (but it will on the second and so on).

This fix guarantees that the checkstyle will be executed AFTER DynamicConstants is generated.  There is a change of behavior that I consider harmless but maybe I am missing something:  the clean of the build package is made before the checkstyle is executed.  This adds an extra second or so to spot errors on checkstyle, but it seems to me cleaner to do a clean and then do the checkstyle (to be sure that no error were introduced in the dynamically generated java files).