Darwin - fix PR c++/87380

Darwin - fix PR c++/87380

This is [intentionally] broken C++ ABI, that was catering for a
tool problem that existed in a very old Darwin toolchain.

The issue is not present after Darwin7 (using default system
tools) so confine the fix to that revision or earlier.

2018-12-06  Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/87380
	* config/darwin.h (TARGET_WEAK_NOT_IN_ARCHIVE_TOC) Remove; use the
	default.
	* config/rs6000/darwin7.h (TARGET_WEAK_NOT_IN_ARCHIVE_TOC): New.

From-SVN: r266866