Add a cross-platform port of cctools.

This basically is binutils for Mac OS X, but ported to work on
(GNU/)Linux and FreeBSD.

And it's up-to-date as well! I'm mentioning this, because it was quite
hard to find a recent port of it and I just accidentally stumbled on it
while trying to do the port by myself.

So thanks to @tpoechtrager for doing this.

Also, I've added two more patches, which essentially are:

 * ld-rpath-nonfinal:
     This allows -rpath to be used for linking non-final builds, which
     was allowed for earlier versions of cctools and got a check for
     that in more recent versions.

 * ld-ignore-rpath-link:
     Ignores the -rpath-link option, because the cross-wrapper uses it
     in different places. Unfortunately, the cctools linker doesn't
     support it, so we might need to implement this later if it's
     possible (I'm not a Mach-O man^H^H^Hexpert).

Signed-off-by: aszlig <aszlig@redmoonstudios.org>