Makefile: avoid infinite loop on configure.ac change

If you are using autoconf and change the configure.ac, the Makefile will notice that config.status is older than configure.ac, and will attempt to rebuild and re-run the configure script to pick up your changes. The first step in doing so is to run "make configure". Unfortunately, this tries to include config.mak.autogen, which depends on config.status, which depends on configure.ac; so we must rebuild config.status. Which leads to us running "make configure", and so on. It's easy to demonstrate with: make configure ./configure touch configure.ac make We can break this cycle by not re-invoking make to build "configure", and instead just putting its rules inline into our config.status rebuild procedure. We can avoid a copy by factoring the rules into a make variable. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>