asan_emit_stack_protection and functions it calls have various asserts that
verify sanity of the stack protection instrumentation.  But, that
verification can easily fail if we've diagnosed a frame offset overflow.
asan_emit_stack_protection just emits some extra code in the prologue,
if we've reported errors, we aren't producing assembly, so it doesn't
really matter if we don't include the protection code, compilation
is going to fail anyway.

2022-11-24  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/107317
	* asan.cc: Include diagnostic-core.h.
	(asan_emit_stack_protection): Return NULL early if seen_error ().

	* gcc.dg/asan/pr107317.c: New test.