If GNU make 3.81 is not found then build it as a companion tool.

Signed-off-by: Ray Donnelly <mingw.android@gmail.com>
[yann.morin.1998@free.fr: add message "checking for make 3.81"]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <8b8bf6998f3d239f6c74.1392920971@advancedsearch.virginmedia.com>
Patchwork-Id: 322302

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

 printf "Done. You may now run:\n    ./configure\n"