Makefile: common-cmds.h depends on generate-cmdlist.sh script

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Makefile

@@ -748,6 +748,8 @@ git-merge-subtree$X: git-merge-recursive$X
 $(BUILT_INS): git$X
 	$(QUIET_BUILT_IN)rm -f $@ && ln git$X $@
 
+common-cmds.h: ./generate-cmdlist.sh
+
 common-cmds.h: $(wildcard Documentation/git-*.txt)
 	$(QUIET_GEN)./generate-cmdlist.sh > $@+ && mv $@+ $@