x86: Define LIBGCC2_UNWIND_ATTRIBUTE on ia32 [PR104781]

On Mon, Mar 07, 2022 at 07:06:28AM -0800, H.J. Lu wrote:
> Since eh_return doesn't work with stack realignment, disable SSE on
> unwind-c.c and unwind-dw2.c to avoid stack realignment with the 4-byte
> incoming stack to avoid SSE usage which is caused by

The following change does that using LIBGCC2_UNWIND_ATTRIBUTE macro instead,
for ia32 only by forcing -mgeneral-regs-only on routines that call
__builtin_eh_return in libgcc.

2022-03-09  Jakub Jelinek  <jakub@redhat.com>

	PR target/104781
	* config/i386/i386.h (LIBGCC2_UNWIND_ATTRIBUTE): Define for ia32.