Simple Makefile fix for rpmbuild

Trying to create a RPM from current CRIU HEAD fails as the crit
installation ignores $(DESTDIR).

This simple patch adds staged installation for crit:

https://github.com/adrianreber/criu/commit/3f7dd400471d717363c143198fe90dc75fac648bSigned-off-by: Pavel Emelyanov <xemul@parallels.com>

Makefile

@@ -314,7 +314,7 @@ install-man:
 
 install-crit: crit
 	$(E) "  INSTALL crit"
-	$(Q) python scripts/crit-setup.py install --prefix=$(PREFIX)
+	$(Q) python scripts/crit-setup.py install --prefix=$(DESTDIR)$(PREFIX)
 
 .PHONY: install install-man install-crit