[arm] Update default CPUs during configure

There are a couple of places in config.gcc where the default CPU is
still arm6, but that was removed as a supported CPU earlier this year.
This patch fixes those entries.

The default CPU for configurations that do not explicitly set a
default is now arm7tdmi (so assumes thumb is available).  Given that
StrongArm is on the deprecated list, this is a better default than we
had previously.

For NetBSD the default is StrongArm; this is the only remaining port
that uses the old ABI and really still carries support for non-thumb
based targets.

	PR target/86383
	* config.gcc (arm*-*-netbsdelf*): Default to StrongARM if no CPU
	specified to configure.
	(arm*-*-*): Use ARM7TDMI as the target CPU if no default provided.

From-SVN: r265420

gcc/ChangeLog

+2018-10-23  Richard Earnshaw  <rearnsha@arm.com>
+
+	PR target/86383
+	* config.gcc (arm*-*-netbsdelf*): Default to StrongARM if no CPU
+	specified to configure.
+	(arm*-*-*): Use ARM7TDMI as the target CPU if no default provided.
+
 2018-10-23  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/87700

gcc/config.gcc

@@ -1134,7 +1134,7 @@ arm*-*-netbsdelf*)
 	tm_file="dbxelf.h elfos.h ${nbsd_tm_file} arm/elf.h arm/aout.h ${tm_file} arm/netbsd-elf.h"
 	extra_options="${extra_options} netbsd.opt netbsd-elf.opt"
 	tmake_file="${tmake_file} arm/t-arm"
-	target_cpu_cname="arm6"
+	target_cpu_cname="strongarm"
 	;;
 arm*-*-linux-*)			# ARM GNU/Linux with ELF
 	tm_file="dbxelf.h elfos.h gnu-user.h linux.h linux-android.h glibc-stdint.h arm/elf.h arm/linux-gas.h arm/linux-elf.h"
@@ -3987,7 +3987,7 @@ case "${target}" in
 				TM_MULTILIB_CONFIG="$with_multilib_list"
 			fi
 		fi
-		target_cpu_cname=${target_cpu_cname:-arm6}
+		target_cpu_cname=${target_cpu_cname:-arm7tdmi}
 		with_cpu=${with_cpu:-$target_cpu_cname}
 		;;