LoongArch: gcc12: Implement option save/restore.

LoongArch: gcc12: Implement option save/restore.

LTO option streaming and target attributes both require per-function
target configuration, which is achieved via option save/restore.

We implement TARGET_OPTION_{SAVE,RESTORE} to switch the la_target
context in addition to other automatically maintained option states
(via the "Save" option property in the .opt files).

	PR target/113233

gcc/ChangeLog:

	* config/loongarch/genopts/loongarch.opt.in: Mark options with
	the "Save" property.
	* config/loongarch/loongarch-opts.cc
	(loongarch_update_gcc_opt_status): Update the value of the
	la_target to global_options.
	* config/loongarch/loongarch-opts.h
	(loongarch_update_gcc_opt_status): Add a function declaration.
	* config/loongarch/loongarch.cc
	(loongarch_option_override_internal): Call the function
	loongarch_update_gcc_opt_status.
	(loongarch_option_save): New functions.
	(loongarch_option_restore): Likewise.
	(TARGET_OPTION_SAVE): Define macro.
	(TARGET_OPTION_RESTORE): Likewise.
	* config/loongarch/loongarch.opt: Regenerate.

(cherry picked from commit ea2a9c76a1dcffbbec6e53655bef9236d3a8e691)