[Darwin, Objective-C] Switch Objective-C meta-data sections properly.

[Darwin, Objective-C] Switch Objective-C meta-data sections properly.

We were emitting the directives to switch, but not recording the change
in varasm. This means that subsequent switches might be omitted (since
varasm incorrectly concludes that the wrong section is current).

2019-09-03  Iain Sandoe  <iain@sandoe.co.uk>

	Backport from mainline
	2019-05-18  Iain Sandoe  <iain@sandoe.co.uk>

	* config/darwin.c (darwin_file_end): Use switch_to_section ()
	instead of direct output of the asm.

From-SVN: r275349