Fix memory chunk corruption for opts_obstack (PR jit/68446)

Fix memory chunk corruption for opts_obstack (PR jit/68446)

gcc/ChangeLog:
	PR jit/68446
	* gcc.c (driver::decode_argv): Add call to
	init_opts_obstack before init_options_struct.
	* opts.c (init_opts_obstack): Remove idempotency.
	(init_options_struct): Replace call to init_opts_obstack
	with a gcc_assert to verify that it has already been called.
	* toplev.c (toplev::main): Add call to init_opts_obstack before
	calls to init_options_struct.
	(toplev::finalize): Move cleanup of opts_obstack next to
	cleanup of save_decoded_options, clearing the latter, and
	save_decoded_options_count.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@232567 138bc75d-0d04-0410-961f-82ee72b054a4