[Toybox] making ./configure executable.

[Rob Landley]

I tried adding this to configure:

if [ "$(basename "$0")" == configure ]
then
  echo "This file is just a persistent place to set environment variables."
  echo "You probably want to run 'make defconfig'."
  echo "Type 'make help' for more options, or see the README."
  exit 1
fi

But if your #!/bin/sh points to the Defective Annoying SHell it
goes "unexpected operator [" EVEN THOUGH "[" IS IN THE $PATH,
and I'm just not going there.

So I've put #!/bin/bash at the top, set the executable bit, and
I'm keeping the complaint to one line and running "make defconfig"
anyway on the theory making it easier to use is better than trying
to educating people with a pop-up window error.

Rob