Common ground work for vxworks7 ports updates

Common ground work for vxworks7 ports updates

2019-11-06  Pat Bernardi  <bernardi@adacore.com>
            Jerome Lambourg  <lambourg@adacore.com>
            Olivier Hainque  <hainque@adacore.com>

	gcc/
	* config.gcc: Add comment to introduce the TARGET_VXWORKS
	commong macro definitions, conveying VXWORKS7 or 64bit general
	variations.  Add a block to set gcc_cv_initfini_array
	unconditionally to "yes" for VxWorks7.
	config/vx-common.h (VXWORKS_CC1_SPEC): New macro, empty string
	by default.  Update some comments.
	config/vxworks.h (VXWORKS_EXTRA_LIBS_RTP): New macro, empty by
	default, to be added the end of VXWORKS_LIBS_RTP.
	(VXWORKS_LIBS_RTP): Replace hardcoded part by VXWORKS_BASE_LIBS_RTP
	and append VXWORKS_EXTRA_LIBS_RTP, both of which specific ports may
	redefine.
	(VXWORKS_NET_LIBS_RTP): Account for VxWorks7 specificities.
	(VXWORKS_CC1_SPEC): Common base definition, with VxWorks7 variation
	to account for the now available TLS abilities.
	(TARGET_LIBC_HAS_FUNCTION): Account for VxWorks7 abilities.
	(VXWORKS_HAVE_TLS): Likewise.

Co-Authored-By: Jerome Lambourg <lambourg@adacore.com>
Co-Authored-By: Olivier Hainque <hainque@adacore.com>
From-SVN: r278247