Makefile: reenable install with NO_CURL

Setting NO_CURL leaves some variables like REMOTE_CURL_ALIASES
empty, which creates no fun when for-looping over
$(REMOTE_CURL_ALIASES) unconditionally. Make it conditional.
Reported-by: NPaul Walker <PWalker752@aol.com>
Signed-off-by: NMichael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Makefile

@@ -1841,12 +1841,13 @@ endif
 		ln -s "git$X" "$$execdir/$$p" 2>/dev/null || \
 		cp "$$execdir/git$X" "$$execdir/$$p" || exit; \
 	  done; } && \
-	{ for p in $(REMOTE_CURL_ALIASES); do \
+	{ test x"$(REMOTE_CURL_ALIASES)" = x || \
+		{ for p in $(REMOTE_CURL_ALIASES); do \
 		$(RM) "$$execdir/$$p" && \
 		ln "$$execdir/git-remote-http$X" "$$execdir/$$p" 2>/dev/null || \
 		ln -s "git-remote-http$X" "$$execdir/$$p" 2>/dev/null || \
 		cp "$$execdir/git-remote-http$X" "$$execdir/$$p" || exit; \
-	  done; } && \
+	  done; } ; } && \
 	./check_bindir "z$$bindir" "z$$execdir" "$$bindir/git-add$X"
 
 install-doc: