devel/aarch64-none-elf-gcc: fix build with libc++ 17

When building relatively recent gcc ports (with C++ in them) against
libc++ 17, you get errors similar to:

  In file included from /wrkdirs/usr/ports/lang/gcc12/work/gcc-12.2.0/gcc/cp/module.cc:208:
  In file included from /wrkdirs/usr/ports/lang/gcc12/work/gcc-12.2.0/gcc/system.h:239:
  In file included from /usr/include/c++/v1/vector:321:
  In file included from /usr/include/c++/v1/__format/formatter_bool.h:20:
  In file included from /usr/include/c++/v1/__format/formatter_integral.h:32:
  In file included from /usr/include/c++/v1/locale:202:
  /usr/include/c++/v1/__locale:546:5: error: '__abi_tag__' attribute only applies to structs, variables, functions, and namespaces
    546 |     _LIBCPP_INLINE_VISIBILITY
        |     ^
  /usr/include/c++/v1/__config:813:37: note: expanded from macro '_LIBCPP_INLINE_VISIBILITY'
    813 | #  define _LIBCPP_INLINE_VISIBILITY _LIBCPP_HIDE_FROM_ABI
        |                                     ^
  /usr/include/c++/v1/__config:792:26: note: expanded from macro '_LIBCPP_HIDE_FROM_ABI'
    792 |           __attribute__((__abi_tag__(_LIBCPP_TOSTRING(_LIBCPP_VERSIONED_IDENTIFIER))))
        |                          ^
  In file included from /wrkdirs/usr/ports/lang/gcc12/work/gcc-12.2.0/gcc/cp/module.cc:208:
  In file included from /wrkdirs/usr/ports/lang/gcc12/work/gcc-12.2.0/gcc/system.h:239:
  In file included from /usr/include/c++/v1/vector:321:
  In file included from /usr/include/c++/v1/__format/formatter_bool.h:20:
  In file included from /usr/include/c++/v1/__format/formatter_integral.h:32:
  In file included from /usr/include/c++/v1/locale:202:
  /usr/include/c++/v1/__locale:547:37: error: expected ';' at end of declaration list
    547 |     char_type toupper(char_type __c) const
        |                                     ^
  /usr/include/c++/v1/__locale:553:48: error: too many arguments provided to function-like macro invocation
    553 |     const char_type* toupper(char_type* __low, const char_type* __high) const
        |                                                ^
  /wrkdirs/usr/ports/lang/gcc12/work/gcc-12.2.0/gcc/../include/safe-ctype.h:146:9: note: macro 'toupper' defined here
    146 | #define toupper(c) do_not_use_toupper_with_safe_ctype
        |         ^

This is because gcc/system.h includes safe-ctype.h which redefines ctype
macros such as toupper, tolower, etc to "poison" them.

However, it should only include the safe-ctype.h header *after* any C++
headers, such as <list>, <map>, <string>, etc, otherwise these might
transitively include internal ctype headers (such as with libc++ 17),
causing the above conflicts.

This commit moves the safe-ctype.h inclusion to later in gcc/system.h,
which solves this issue, and makes it possible to build against libc++
17.

PR:		274040
Approved by:	manu (maintainer)
MFH:		2023Q3

devel/aarch64-none-elf-gcc/files/patch-gcc_system.h

@@ -0,0 +1,42 @@
+--- gcc/system.h.orig	2022-04-21 07:58:53 UTC
++++ gcc/system.h
+@@ -203,19 +203,6 @@ extern int fprintf_unlocked (FILE *, const char *, ...
+ #endif
+ #endif
+
+-/* There are an extraordinary number of issues with <ctype.h>.
+-   The last straw is that it varies with the locale.  Use libiberty's
+-   replacement instead.  */
+-#include "safe-ctype.h"
+-
+-#include <sys/types.h>
+-
+-#include <errno.h>
+-
+-#if !defined (errno) && defined (HAVE_DECL_ERRNO) && !HAVE_DECL_ERRNO
+-extern int errno;
+-#endif
+-
+ #ifdef __cplusplus
+ #if defined (INCLUDE_ALGORITHM) || !defined (HAVE_SWAP_IN_UTILITY)
+ # include <algorithm>
+@@ -242,6 +229,19 @@ extern int errno;
+ # include <new>
+ # include <utility>
+ # include <type_traits>
++#endif
++
++/* There are an extraordinary number of issues with <ctype.h>.
++   The last straw is that it varies with the locale.  Use libiberty's
++   replacement instead.  */
++#include "safe-ctype.h"
++
++#include <sys/types.h>
++
++#include <errno.h>
++
++#if !defined (errno) && defined (HAVE_DECL_ERRNO) && !HAVE_DECL_ERRNO
++extern int errno;
+ #endif
+
+ /* Some of glibc's string inlines cause warnings.  Plus we'd rather