elfutils: disable -Werror to fix the build

  nm.c: In function 'show_symbols_sysv':
  nm.c:773:27: error: argument to 'sizeof' in 'snprintf' call is the same expression as the destination; did you mean to provide an explicit length? [-Werror=sizeof-pointer-memaccess]
      snprintf (name, sizeof name, "[invalid sh_name %#" PRIx32 "]",
                             ^
  cc1: all warnings being treated as errors