[ARC] Enable init_array support.

gcc's common configure script has a subtle flaw that it only tests
{init,fini.preinit}_array support when NOT cross compiling. This causes
cross builds to erroneously deduce that the feature is not supported by
the target.

| host-gcc-final-ab544139bfee/build/gcc/config.log
|
|configure:22941: checking for .preinit_array/.init_array/.fini_array support
|configure:23106: checking cross compile... guessing
|configure:23111: result: no

The right fix is to enable this for *all* cross setups (and address any
fallouts). However in the short-term to enable ARC glibc port to upstream,
force enable this for ARC.

This has been discussed at length on glibc mailing list [1], [2]

[1] https://sourceware.org/ml/libc-alpha/2018-11/msg00870.html
[2] https://sourceware.org/ml/libc-alpha/2019-01/msg00656.html

gcc/

2019-xx-xx  Vineet Gupta <vgupta@synopsys.com>

	* gcc/config.gcc: Force .init_array for ARC

From-SVN: r268365

gcc/ChangeLog

+2019-01-29  Vineet Gupta  <vgupta@synopsys.com>
+
+	* gcc/config.gcc: Force .init_array for ARC.
+
 2019-01-29  Richard Biener  <rguenther@suse.de>
 
 	PR debug/87295

gcc/config.gcc

@@ -1110,7 +1110,10 @@ arc*-*-linux*)
 	case ${with_endian} in
 	big*)	tm_file="arc/big.h ${tm_file}"
 	esac
-        ;;
+	# Force .init_array support.  The configure script cannot always
+	# automatically detect that GAS supports it, yet we require it.
+	gcc_cv_initfini_array=yes
+	;;
 arm-wrs-vxworks|arm-wrs-vxworks7)
 	extra_options="${extra_options} arm/vxworks.opt"
 	tmake_file="${tmake_file} arm/t-arm arm/t-vxworks"