Makefile: tighten git-http-{fetch,push} dependencies

Although our "git-%$X:" implicit target had dependency on
$(GITLIBS) which included xdiff/lib.a, git-http-{fetch,push} had
their own building rules and with an obsolete dependency on
$(LIB_FILES).  Update the rules to depend on $(GITLIBS), to make
parallel build work correctly.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -587,11 +587,11 @@ git-ssh-push$X: rsh.o
 git-imap-send$X: imap-send.o $(LIB_FILE)
 
 http.o http-fetch.o http-push.o: http.h
-git-http-fetch$X: fetch.o http.o http-fetch.o $(LIB_FILE)
+git-http-fetch$X: fetch.o http.o http-fetch.o $(GITLIBS)
 	$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \
 		$(LIBS) $(CURL_LIBCURL) $(EXPAT_LIBEXPAT)
 
-git-http-push$X: revision.o http.o http-push.o $(LIB_FILE)
+git-http-push$X: revision.o http.o http-push.o $(GITLIBS)
 	$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \
 		$(LIBS) $(CURL_LIBCURL) $(EXPAT_LIBEXPAT)