cctools-port: Pass through wrapped XCToolchain.

At the moment, this includes only dyldinfo, dwarfdump and dsymutil, but
we'll see whether we need more of these utilities later.

Tho reason those are wrapped in cctools-port is because it is the
binutils used to cross-compile for Mac OS X.

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