extras: libtool depends on automake, which in turn depends on autoconf

This solves long-standing conflicts with homebrew as well as the latest Xcode releases. Additionally, in most cases, all 3 items were built anyway.

extras/tools/tools.mak

@@ -84,7 +84,7 @@ libtool: libtool-$(LIBTOOL_VERSION).tar.gz
 	$(UNPACK)
 	$(MOVE)
 
-.libtool: libtool
+.libtool: libtool .automake
 	(cd $<; ./configure --prefix=$(PREFIX) && $(MAKE) && $(MAKE) install)
 	ln -sf libtool $(PREFIX)/bin/glibtool
 	ln -sf libtoolize $(PREFIX)/bin/glibtoolize