- in case one redefines DESTDIR in make install, one gets strange paths:
 $ make install -n DESTDIR=/usr/local/sage-2.8.7
 ...
 cp /usr/local/sage-2.8.7/usr/local/sage/sage /usr/local/sage-2.8.7/usr/bin/
 (I would expect at least 'usr' to disappear.)