multilib_header: Update wrapper to handle arm 32/64 bit
Having arm 32/64 bit headers coexisting turns out to be tricky. Unfortunately
our wrapper works using wordsize.h and this differs on arm so we can't use it.
Therefore replicate the logic here for arm. I did look into writing our
own wordsize.h but we also need to remap kernel headers on arm and
since wordsize.h comes from libc, that doesn't work for kernel headers.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
