middle-end/105537 - debug processing

middle-end/105537 - debug processing

The following makes sure to have a consistent state of
flag_var_tracking_assignments with the distributed handling
in process_options and finish_options by moving everything to
finish_options which also restores diagnostics for
-g0 -fvar-tracking which was lost with previous changes.

2022-05-10  Richard Biener  <rguenther@suse.de>

	PR middle-end/105537
	* toplev.cc (process_options): Move flag_var_tracking
	handling ...
	* opts.cc (finish_options): ... here.

	* gcc.dg/torture/pr105537.c: New testcase.

(cherry picked from commit 76db543db88727789a6c117608a23edc2eace713)