aarch64: Add support for aarch64-gnu (GNU/Hurd on AArch64)

Coupled with a corresponding binutils patch, this produces a toolchain that can
sucessfully build working binaries targeting aarch64-gnu.

gcc/Changelog:

	* config.gcc: Recognize aarch64*-*-gnu* targets.
	* config/aarch64/aarch64-gnu.h: New file.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>

gcc/config.gcc

@@ -1265,6 +1265,12 @@ aarch64*-*-linux*)
 	done
 	TM_MULTILIB_CONFIG=`echo $TM_MULTILIB_CONFIG | sed 's/^,//'`
 	;;
+aarch64*-*-gnu*)
+        tm_file="${tm_file} elfos.h gnu-user.h gnu.h glibc-stdint.h"
+        tm_file="${tm_file} aarch64/aarch64-elf.h aarch64/aarch64-errata.h aarch64/aarch64-gnu.h"
+        tmake_file="${tmake_file} aarch64/t-aarch64"
+        tm_defines="${tm_defines}  TARGET_DEFAULT_ASYNC_UNWIND_TABLES=1"
+	;;
 aarch64*-wrs-vxworks*)
         tm_file="${tm_file} elfos.h aarch64/aarch64-elf.h"
         tm_file="${tm_file} vx-common.h vxworks.h aarch64/aarch64-vxworks.h"

gcc/config/aarch64/aarch64-gnu.h

@@ -0,0 +1,68 @@
+/* Definitions for AArch64 running GNU/Hurd.
+   Copyright (C) 2009-2024 Free Software Foundation, Inc.
+
+   This file is part of GCC.
+
+   GCC is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   GCC is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with GCC; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_AARCH64_GNU_H
+#define GCC_AARCH64_GNU_H
+
+#define GNU_USER_DYNAMIC_LINKER "/lib/ld-aarch64%{mbig-endian:_be}%{mabi=ilp32:_ilp32}.so.1"
+
+#define CPP_SPEC "%{pthread:-D_REENTRANT}"
+
+#define GNU_TARGET_LINK_SPEC  "%{h*}		\
+   %{static:-Bstatic}				\
+   %{shared:-shared}				\
+   %{symbolic:-Bsymbolic}			\
+   %{!static:%{!static-pie:			\
+     %{rdynamic:-export-dynamic}		\
+     %{!shared:-dynamic-linker " GNU_USER_DYNAMIC_LINKER "}}} \
+   %{static-pie:-Bstatic -pie --no-dynamic-linker -z text} \
+   -X						\
+   %{mbig-endian:-EB} %{mlittle-endian:-EL}     \
+   -maarch64gnu%{mabi=ilp32:32}%{mbig-endian:b}"
+
+
+#define LINK_SPEC GNU_TARGET_LINK_SPEC AARCH64_ERRATA_LINK_SPEC
+
+#define GNU_USER_TARGET_MATHFILE_SPEC \
+  "%{Ofast|ffast-math|funsafe-math-optimizations:%{!shared:crtfastmath.o%s}}"
+
+#undef ENDFILE_SPEC
+#define ENDFILE_SPEC   \
+  GNU_USER_TARGET_MATHFILE_SPEC " " \
+  GNU_USER_TARGET_ENDFILE_SPEC
+
+#define TARGET_OS_CPP_BUILTINS()		\
+  do						\
+    {						\
+	GNU_USER_TARGET_OS_CPP_BUILTINS();	\
+    }						\
+  while (0)
+
+#define TARGET_ASM_FILE_END aarch64_file_end_indicate_exec_stack
+
+/* Uninitialized common symbols in non-PIE executables, even with
+   strong definitions in dependent shared libraries, will resolve
+   to COPY relocated symbol in the executable.  See PR65780.  */
+#undef TARGET_BINDS_LOCAL_P
+#define TARGET_BINDS_LOCAL_P default_binds_local_p_2
+
+/* Define this to be nonzero if static stack checking is supported.  */
+#define STACK_CHECK_STATIC_BUILTIN 1
+
+#endif  /* GCC_AARCH64_GNU_H */