Copy existing javaclasses from build dir to current dist dir.

def distribute_javaclasses(self, javaclass_dir, dest_dir="src"):
        '''Copy existing javaclasses from build dir to current dist dir.'''
        info('Copying java files')
        ensure_dir(dest_dir)
        for filename in glob.glob(javaclass_dir):
            shprint(sh.cp, '-a', filename, dest_dir)