Fix the binutils version.

The version of binutils used by this script doesn't exist on
kernel.org, which is where it tries to fetch it from.  Replace
it with the closest version that actually exists.
Check for /usr/local/include as well as /opt/local/include.
Fix handling of --src-dir.
Fix compiler warnings.
Add support for FreeBSD.
Add a script to set up FreeBSD.

Add a script that configures a FreeBSD system to be able to build
a UEFI ROM image.
Add local config files.
Ignore files created by the build process.