GCC arc port defaults to -fcommon

[Florian Weimer via Gcc]

It seems to me that the arc port still defaults to -fcommon, presumably
due to this in gcc/common/config/arc/arc-common.c:

static void
arc_option_init_struct (struct gcc_options *opts)
{
  opts->x_flag_no_common = 255; /* Mark as not user-initialized.  */

  /* Which cpu we're compiling for (ARC600, ARC601, ARC700, ARCv2).  */
  arc_cpu = PROCESSOR_NONE;
}

Is that really necessary?  Is -fno-common broken on arc?

I plan to switch glibc to build with -fno-common unconditionally, for
all GCC versions and architectures, and I wonder if that would be a
blocker.

Thanks,
Florian