diagnostics/output-spec.cc: simplify implementation

diagnostics/output-spec.cc: simplify implementation

No functional change intended.

gcc/ChangeLog:
	* diagnostics/output-spec.cc (sarif_scheme_handler::make_sink):
	Populate sarif_generation_options instance directly, rather than
	through local variables.
	(sarif_scheme_handler::make_sarif_gen_opts): Drop.
	(html_scheme_handler::make_sink): Populate html_generation_options
	instance directly, rather than through local variables.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>