gcc-final: hard link TARGET-cc -> TARGET-gcc

Doing a symlink results in incorrect behavior:

    $ x86_64-buildroot-linux-gnux32-cc
    --version
    ccache: error: execv of [...]/x86_64-buildroot-linux-gnux32-cc.br_real.br_real failed: No such file or directory

    $ x86_64-buildroot-linux-gnux32-gcc --version
    x86_64-buildroot-linux-gnux32-gcc.br_real (Buildroot 2015.11-git-00965-g8d89653-dirty) 5.2.0
    Copyright (C) 2015 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions.  There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Note the double .br_real on the invocation by toolchain-wrapper.

[Thomas: use 'ln -f' instead of 'cp -l', as suggested by Arnout.]

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>