lang/gcc12: Fix SIGBUS depending on CPUTYPE

Compiling GCC with some CPUTYPE values (e.g. broadwell) result in
breaking some applications (e.g. math/octave, cad/freecad), sending a
SIGBUS.

The issue is due to GCC generating instructions that require variables
to be aligned in memory on certain CPUs. Our libthr does not have the
required alignment so these CPUs fail to execute these instructions.

The patch disables the generation of such instructions.

PR:             285711
Reported by:    cracauer
Tested by:      cracauer, jbo

lang/gcc12/Makefile

@@ -1,6 +1,6 @@
 PORTNAME=	gcc
 PORTVERSION=	12.4.0
-PORTREVISION=	2
+PORTREVISION=	3
 CATEGORIES=	lang
 MASTER_SITES=	GCC
 PKGNAMESUFFIX=	${SUFFIX}

lang/gcc12/files/patch-libgcc_unwind.inc

@@ -0,0 +1,28 @@
+GCC generates instructions that require variables to be aligned in memory on
+certain CPUs. Our libthr does not have the required alignment so these CPUs fail
+to execute these instructions. The instructions generation is driven by CPUTYPE.
+Some CPUs are fine to execute these instructions on unaligned data.
+
+This patch explicitly forbids GCC to generate instructions that require
+alignment of the data.
+
+If the entire program is compiled by LLVM or GCC, there is no problem (with GCC
+everything is aligned, with LLVM vmovdqa is not used to assign both variables
+at once).
+
+Linux does not have libthr, so Linux is not affected. Moreover Linux is likely
+to build everything with GCC.
+
+--- libgcc/unwind.inc.orig	2025-04-12 08:18:17 UTC
++++ libgcc/unwind.inc
+@@ -212,8 +212,8 @@ _Unwind_ForcedUnwind (struct _Unwind_Exception *exc,
+   uw_init_context (&this_context);
+   cur_context = this_context;
+ 
+-  exc->private_1 = (_Unwind_Ptr) stop;
+-  exc->private_2 = (_Unwind_Ptr) stop_argument;
++  __builtin_memcpy(&exc->private_1, &stop, sizeof(_Unwind_Ptr));
++  __builtin_memcpy(&exc->private_2, &stop_argument, sizeof(_Unwind_Ptr));
+ 
+   code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context, &frames);
+   if (code != _URC_INSTALL_CONTEXT)