Enable ifunc attribute by default for ARM GNU/Linux

Similar to other architectures with IFUNC binutils/glibc support, this
patch enables the ifunc attribute for ARM GNU/Linux.  Although not
required for build master GLIBC, the intention is to allow refactor
its assembly implementation to C.

Tested compilation of glibc (in conjunction with a glibc patch to
support using the attribute on ARM) with build-many-glibcs.py (with
a patch to add a armv7 variant which enables multiarch).  I have
not run the GCC tests for ARM.

	* config.gcc (default_gnu_indirect_function): Default to yes for
	arm*-*-linux* with glibc.

From-SVN: r253635

gcc/ChangeLog

+2017-10-11  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+
+	* config.gcc (default_gnu_indirect_function): Default to yes for
+	arm*-*-linux* with glibc.
+
 2017-10-11  Richard Biener  <rguenther@suse.de>
 
 	* tree-scalar-evolution.c (get_scalar_evolution): Handle

gcc/config.gcc

@@ -3108,7 +3108,7 @@ case ${target} in
         ;;
 *-*-linux*)
 	case ${target} in
-	aarch64*-* | i[34567]86-* | powerpc*-* | s390*-* | sparc*-* | x86_64-*)
+	aarch64*-* | arm*-* | i[34567]86-* | powerpc*-* | s390*-* | sparc*-* | x86_64-*)
 		default_gnu_indirect_function=yes
 		;;
 	esac