Makefile: add .PHONY dependency

Enough wasted time on a random 'all' file... Thanks Andres and Josh!

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/Makefile b/Makefile
index abfeac1..c761604 100644
--- a/Makefile
+++ b/Makefile
@@ -13,6 +13,9 @@
 	@$(MAKE) -C test
 	@$(MAKE) -C examples
 
+.PHONY: all install default clean test
+.PHONY: FORCE cscope
+
 partcheck: all
 	@echo "make partcheck => TODO add tests with out kernel support"