toolchain: fix binutils broken symlink

The Makefile for binutils creates a broken symlink to "binutils-linaro" in
"trunk/build_dir/toolchain-<target>_gcc-4.9-linaro_uClibc-0.9.33.2".
Modify the Makefile to point the symlink to the correct directory.

Signed-off-by: Nathan Hintz <nlhintz@hotmail.com>

SVN-Revision: 42954