Update the arm-*-vxworks* support

Update the arm-*-vxworks* support

2019-11-13  Jerome Lambourg  <lambourg@adacore.com>
            Doug Rupp <rupp@adacore.com>
            Olivier Hainque  <hainque@adacore.com>

	gcc/
	* config.gcc: Collapse the arm-vxworks entries into
	a single arm-wrs-vxworks7* one, bpabi based.  Update
	the default cpu from arm8 to armv7-a
	* config/arm/vxworks.h (CC1_SPEC): Simplify, knowing that
	we always use ARM_UNWIND_INFO.
	(DWARF2_UNWIND_INFO): Remove redefinition.
	(ARM_TARGET2_DWARF_FORMAT): Likewise.
	(VXWORKS_PERSONALITY): Define, to "llvm".
	(VXWORKS_EXTRA_LIBS_RTP): Define, to "-lllvm".

	libgcc/
	* config.host: Collapse the arm-vxworks entries into
	a single arm-wrs-vxworks7* one.
	* config/arm/unwind-arm-vxworks.c: Update comments.  Provide
	__gnu_Unwind_Find_exidx and a weak dummy __cxa_type_match for
	kernel modules, to be overriden by libstdc++ when we link with
	it.  Rely on externally provided __exidx_start/end.

Co-Authored-By: Doug Rupp <rupp@adacore.com>
Co-Authored-By: Olivier Hainque <hainque@adacore.com>
From-SVN: r278253