Arm: Fix incorrect tailcall-generation for indirect calls [PR113780]

This patch fixes a bug that causes indirect calls in PAC-enabled functions
to be tailcalled incorrectly when all argument registers R0-R3 are used.

2024-02-07  Tejas Belagod  <tejas.belagod@arm.com>

	PR target/113780
	* config/arm/arm.cc (arm_function_ok_for_sibcall): Don't allow tailcalls
	for indirect calls with 4 or more arguments in pac-enabled functions.

	* lib/target-supports.exp (v8_1m_main_pacbti): Add __ARM_FEATURE_PAUTH.
	* gcc.target/arm/pac-sibcall.c: New.