aarch64: Introduce indirect_return attribute

aarch64: Introduce indirect_return attribute

Tail calls of indirect_return functions from non-indirect_return
functions are disallowed even if BTI is disabled, since the call
site may have BTI enabled.

Needed for swapcontext within the same function when GCS is enabled.

gcc/ChangeLog:

	* config/aarch64/aarch64.cc (aarch64_gnu_attributes): Add
	indirect_return.
	(aarch64_gen_callee_cookie): Use indirect_return attribute.
	(aarch64_callee_indirect_return): New.
	(aarch_fun_is_indirect_return): New.
	(aarch64_function_ok_for_sibcall): Disallow tail calls if caller
	is non-indirect_return but callee is indirect_return.
	(aarch64_function_arg): Add indirect_return to cookie.
	(aarch64_init_cumulative_args): Record indirect_return in
	CUMULATIVE_ARGS.
	(aarch64_comp_type_attributes): Check indirect_return attribute.
	(aarch64_output_mi_thunk): Add indirect_return to cookie.
	* config/aarch64/aarch64.h (CUMULATIVE_ARGS): Add new field
	indirect_return.
	* config/aarch64/aarch64.md (tlsdesc_small_<mode>): Update.
	* config/aarch64/aarch64-opts.h (AARCH64_NUM_ABI_ATTRIBUTES): New.
	* config/aarch64/aarch64-protos.h (aarch64_gen_callee_cookie): Update.
	* config/arm/aarch-bti-insert.cc (call_needs_bti_j): New.
	(rest_of_insert_bti): Use call_needs_bti_j.
	* config/arm/aarch-common-protos.h
	(aarch_fun_is_indirect_return): New.
	* config/arm/arm.cc
	(aarch_fun_is_indirect_return): New.

Co-authored-by: Yury Khrustalev <yury.khrustalev@arm.com>