Kbuild, lto: Add a gcc-ld script to let run gcc as ld

For LTO we need to run the link step with gcc, not ld.
Since there are a lot of linker options passed to it, add a gcc-ld wrapper
that wraps them as -Wl,

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1391846481-31491-10-git-send-email-ak@linux.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>