Correct installation to follow standards

DESTDIR is usually empty, it is used by packaging tools to create an install into a temporary directory, to create a tarball that will then be extracted into the real root directory.

'cp' is incorrect for installing programs. Among other things, it will fail (with ETXTBUSY) if the program already installed is currently in use.

Directories must be created before you install files into them (an empty DESTDIR makes this fail most obviously).