Aarch64 sim fix for gcc-10 miscompilation.

Aarch64 sim fix for gcc-10 miscompilation.

This fixes a problem that occurs when compiled by gcc-10, as the code
is relying on undefined overflow behavior.  This is fixed by replacing
compares between 32-bit and 64-bit results with compares that just use
the 64-bit results with a cast.

	PR sim/27483
	* simulator.c (set_flags_for_add32): Compare uresult against
	itself.  Compare sresult against itself.