makefile: Don't remove PKG-INFO in clean target
tree3517e4ce22dae171bf587c0e1b934d3ad07d27f5
drwxr-xr-x - .tx
-rw-r--r-- 35147 COPYING
-rw-r--r-- 138 MANIFEST.in
-rw-r--r-- 10673 README
drwxr-xr-x - bin
-rw-r--r-- 4820 makefile
drwxr-xr-x - po
-rw-r--r-- 7432 setup.py
drwxr-xr-x - share
drwxr-xr-x - src
drwxr-xr-x - tools