[arm] Rework multilib support

It looks like the fuchsia port relied on inheriting the multilib rules from
the bare-metal port (the t-arm-elf makefile fragment), but that has now been
rewritten on the assuption that the base architecture is ARMv4t; fuchsia
has a base architecture of ARMv7-a.

To account for this, I've cloned the original t-arm-elf rules into a
new makefile fragment t-fuchsia and arranged for that to be used when
targetting this system.

	* config/arm/t-fuchsia: New file.
	* config.gcc (arm*-*-fuchsia*): Use it.

From-SVN: r249305

gcc/ChangeLog

 2017-06-16  Richard Earnshaw  <rearnsha@arm.com>
 
+	* config/arm/t-fuchsia: New file.
+	* config.gcc (arm*-*-fuchsia*): Use it.
+
+2017-06-16  Richard Earnshaw  <rearnsha@arm.com>
+
 	* config/arm/t-symbian: Rewrite for new option infrastructure.
 
 2017-06-16  Richard Earnshaw  <rearnsha@arm.com>

gcc/config.gcc

@@ -1160,7 +1160,7 @@ arm*-*-eabi* | arm*-*-symbianelf* | arm*-*-rtems* | arm*-*-fuchsia*)
 	  ;;
 	arm*-*-fuchsia*)
 	  tm_file="${tm_file} fuchsia.h arm/fuchsia-elf.h glibc-stdint.h"
-	  tmake_file="${tmake_file} arm/t-bpabi"
+	  tmake_file="${tmake_file} arm/t-bpabi arm/t-fuchsia"
 	  target_cpu_cname="generic-armv7-a"
 	  ;;
 	arm*-*-rtems*)

gcc/config/arm/t-fuchsia

+# Copyright (C) 2017 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/>.
+
+# Reset all the multilib variables.
+MULTILIB_OPTIONS	=
+MULTILIB_DIRNAMES	=
+MULTILIB_EXCEPTIONS	=
+MULTILIB_REUSE		=
+MULTILIB_MATCHES	=
+MULTILIB_REQUIRED	=
+
+# For compatibility with gcc-7 we build the following multilibs
+MULTILIB_OPTIONS	+= marm/mthumb
+MULTILIB_DIRNAMES	+= arm thumb
+
+MULTILIB_OPTIONS	+= mfloat-abi=hard
+MULTILIB_DIRNAMES	+= fpu
+MULTILIB_EXCEPTIONS	+= *mthumb/*mfloat-abi=hard*