scripts: unset LIBRARY_PATH and LPATH

These environment variables set search path for gcc at link time, which can break the build.

Signed-off-by: Erik Inge Bolsø <knan-ct@anduin.net>
Message-Id: <alpine.BSF.2.00.1205130131550.21551@anduin.net>
PatchWork-Id: 186872

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

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