use thread_local for ntoa buf

*** 1133,1143 ****
  BUILD.s=        $(AS) $(ASFLAGS) $< -o $@
  
  # Override this top level flag so the compiler builds in its native
  # C99 mode.  This has been enabled to support the complex arithmetic
  # added to libc.
! CSTD=   $(CSTD_GNU99)
  
  # libc method of building an archive
  # The "$(GREP) -v ' L '" part is necessary only until
  # lorder is fixed to ignore thread-local variables.
  BUILD.AR= $(RM) $@ ; \
--- 1133,1143 ----
  BUILD.s=        $(AS) $(ASFLAGS) $< -o $@
  
  # Override this top level flag so the compiler builds in its native
  # C99 mode.  This has been enabled to support the complex arithmetic
  # added to libc.
! CSTD=   $(CSTD_GNU11)
  
  # libc method of building an archive
  # The "$(GREP) -v ' L '" part is necessary only until
  # lorder is fixed to ignore thread-local variables.
  BUILD.AR= $(RM) $@ ; \