Hello,

This adjusts vx-common.h to #define DWARF2_UNWIND_INFO to 0
when ARM_UNWIND_INFO is set, preventing defaults.h from
possibly setting DWARF2_UNWIND_INFO to 1 (as well) on its own
afterwards if the macro isn't defined.

We have been using this for a while in gcc-11 development
toolchains for a variety of VxWorks targets, including arm
and aarch64, and I have performed a couple of sanity check
build for ppc64-vx7r2 and arm-vx7r2 with gcc-12. 

Committing to mainline where the patch applies as-is and
where the close context (defaults.h defining DWARF2_UNWIND_INFO)
hasn't changed.

Cheers,

Olivier

2022-03-10  Olivier Hainque  <hainque@adacore.com>

gcc/
        * config/vx-common.h (DWARF2_UNWIND_INFO): #define to 0
        when ARM_UNWIND_INFO is set.