ia64 seems to be affected too, but the backend doesn't have any
-Wpsabi warnings and I'm not sure if we really need them for an (almost?)
dead target.

2020-04-22  Jakub Jelinek  <jakub@redhat.com>

	PR target/94706
	* config/ia64/ia64.c (hfa_element_mode): Ignore
	cxx17_empty_base_field_p fields.