make: unifdef SUN5_0 (defined)

*** 88,100 ****
  Name            dollarless_value;
  Envvar          envvar;
  #ifdef lint
  char            **environ;
  #endif
- #ifdef SUN5_0
  int             exit_status;
- #endif
  wchar_t         *file_being_read;
  /* Variable gnu_style=true if env. var. SUN_MAKE_COMPAT_MODE=GNU (RFE 4866328) */
  Boolean         gnu_style = false;
  Name_set        hashtab;
  Name            host_arch;
--- 88,98 ----