Disable -Wunused-function under xlC.
Disable -Wunused-function under xlC.

This bug is entirely too verbose.

Bug 2740315

Reviewed-by: Bryce Adelstein Lelbach aka wash <2f0f95f95a80179c2180af4c82f6ea311b6bd2c8@gmail.com>

thrust/thrust,jaredhoberock/thrust,thrust/thrust,andrewcorrigan/thrust-multi-permutation-iterator,thrust/thrust,andrewcorrigan/thrust-multi-permutation-iterator,andrewcorrigan/thrust-multi-permutation-iterator,jaredhoberock/thrust,thrust/thrust,jaredhoberock/thrust,jaredhoberock/thrust,jaredhoberock/thrust,thrust/thrust