middle-end/103038 - avoid ICE with -ftrivial-auto-var-init=pattern

middle-end/103038 - avoid ICE with -ftrivial-auto-var-init=pattern

This avoids ICEing with expanding a VIEW_CONVERT_EXRP of a SSA name
on the LHS by making sure we can native-interpret OFFSET_TYPE and
by never building such a LHS but instead view-converting the RHS
for SSA LHS.

2021-11-02  Richard Biener  <rguenther@suse.de>

	PR middle-end/103038
	* fold-const.c (native_interpret_expr): Handle OFFSET_TYPE.
	(can_native_interpret_type_p): Likewise.
	* internal-fn.c (expand_DEFERRED_INIT): View-convert the
	RHS if the LHS is an SSA name.

	* g++.dg/pr103038.C: New testcase.