Set installation root dir from setup.py

Author: rffontenelle

Makefile.am

@@ -63,7 +63,7 @@ all-local: .stamp-distutils-in-builddir config.py cupshelpers/config.py
 
 # Use distutils to install the module.
 install-exec-local: .stamp-distutils-in-builddir
-	$(PYTHON) setup.py install --prefix=$(DESTDIR)$(prefix)
+	$(PYTHON) setup.py install --root=$(DESTDIR) --prefix=$(DESTDIR)$(prefix)
 
 # Uninstall the module, crossing our fingers that we know enough
 # about how distutils works to do this.  Unfortunately, distutils