[arm64] Fix GCC build issue for CFI

GCC doesn't accept 'lr' in inline assembly, specifically for the
list of clobbered registers. Change all uses to 'x30', for
consistency.

Bug: v8:10026
Change-Id: I5654fee4ca398dfdd99c34d09fc5294d169a9bd8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3693701Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/main@{#80980}

src/execution/arm64/pointer-authentication-arm64.h

@@ -47,15 +47,17 @@ V8_INLINE Address PointerAuthentication::StripPAC(Address pc) {
 #ifdef USE_SIMULATOR
   return Simulator::StripPAC(pc, Simulator::kInstructionPointer);
 #else
+  // x30 == lr, but use 'x30' instead of 'lr' below, as GCC does not accept
+  // 'lr' in the clobbers list.
   asm volatile(
-      "  mov x16, lr\n"
-      "  mov lr, %[pc]\n"
+      "  mov x16, x30\n"
+      "  mov x30, %[pc]\n"
       "  xpaclri\n"
-      "  mov %[pc], lr\n"
-      "  mov lr, x16\n"
+      "  mov %[pc], x30\n"
+      "  mov x30, x16\n"
       : [pc] "+r"(pc)
       :
-      : "x16", "lr");
+      : "x16", "x30");
   return pc;
 #endif
 }