[ARC] Enable init_array support.

[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