Fix frame pointer alignment check.

The frame pointer sanity check in NextStackFrame() was more restrictive than it is necessary. The frame pointer is used to load the saved link-register and the address for the next stack frame. So it only needs to be 8-byte aligned. The aarch64 ABI does not specify an alignment requirement for the frame point.

PiperOrigin-RevId: 463368519
Change-Id: I473e05181603288f14734fe29013900c7505e201

absl/debugging/internal/stacktrace_aarch64-inl.inc

@@ -110,8 +110,8 @@ static void **NextStackFrame(void **old_frame_pointer, const void *uc) {
   }
 #endif
 
-  // aarch64 ABI requires stack pointer to be 16-byte-aligned.
-  if ((reinterpret_cast<uintptr_t>(new_frame_pointer) & 15) != 0)
+  // The frame pointer should be 8-byte aligned.
+  if ((reinterpret_cast<uintptr_t>(new_frame_pointer) & 7) != 0)
     return nullptr;
 
   // Check frame size.  In strict mode, we assume frames to be under