cc-gcc: the frontends are responsible for mkdir/chdir

The build dir are created depending on the host (host for that specific
backend, not host for the toolchain). Only the frontends know what host
this is, so only the frontends can create non-ambiguous dirs.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

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