Makefile: change order of dirs and dependencies

If during the dependencies step, a package needs to be downloaded, the
download directory already has to be present. If not, the file will be
downloaded under the name 'dl' instead of in the directory 'dl'.

This patch changes the order of dirs and dependencies in the world target to
fix this.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>