LTO/WPA: Ensure that output_offload_tables only writes table once [PR116535]

When ltrans was written concurrently, e.g. via -flto=N (N > 1, assuming
sufficient partiations, e.g., via -flto-partition=max), output_offload_tables
wrote the output tables once per fork.

	PR lto/116535

gcc/ChangeLog:

	* lto-cgraph.cc (output_offload_tables): Remove offload_ frees.
	* lto-streamer-out.cc (lto_output): Make call to it depend on
	lto_get_out_decl_state ()->output_offload_tables_p.
	* lto-streamer.h (struct lto_out_decl_state): Add
	output_offload_tables_p field.
	* tree-pass.h (ipa_write_optimization_summaries): Add bool argument.
	* passes.cc (ipa_write_summaries_1): Add bool
	output_offload_tables_p arg.
	(ipa_write_summaries): Update call.
	(ipa_write_optimization_summaries): Accept output_offload_tables_p.

gcc/lto/ChangeLog:

	* lto.cc (stream_out): Update call to
	ipa_write_optimization_summaries to pass true for first partition.