[PATCH 3/15] arm: Add option -mbranch-protection

[PATCH 3/15] arm: Add option -mbranch-protection

Add -mbranch-protection option.  This option enables the
code-generation of pointer signing and authentication instructions in
function prologues and epilogues.

gcc/ChangeLog:

	* config/arm/arm.cc (arm_configure_build_target): Parse and validate
	-mbranch-protection option and initialize appropriate data structures.
	* config/arm/arm.opt (-mbranch-protection): New option.
	* doc/invoke.texi (Arm Options): Document it.

Co-Authored-By: Tejas Belagod  <tbelagod@arm.com>
Co-Authored-By: Richard Earnshaw <Richard.Earnshaw@arm.com>