Need a slash after CROSS_BINUTILS_PREFIX
/usr/local/include isn't special on FreeBSD.

On FreeBSD, we may not automatically pick up includes in /usr/local/include or libraries in /usr/local/lib, so we might need to specify them explicitly.
Pass extra information to llvm-lit on FreeBSD.

Because of the /usr/local/lib thing, we need to provide a little more information.