cc/gcc: remove duplicate code in core pass-1

Whatever the threading model (NPTL, LT...), we build the same
core pass-1 compiler, so there is no need to have a case-esac
construct.

Remove now mis-leading and incorect comment.

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

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

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