This fixlet makes sure -mcpu=xscale selects the correct VX_CPU.

Fixes a number of tests for arm-vxworks.

Committing to mainline shortly.

Olivier


2020-09-24  Olivier Hainque  <hainque@adacore.com>

        * config/arm/vxworks.h (TARGET_OS_CPP_BUILTINS): Fix
        the VX_CPU selection for -mcpu=xscale on arm-vxworks.