os::current_stack_pointer has many varying implementations, some of which are erroneous. Additionally, this does not play well with Link Time Optimization, which often inlines the method into the caller, causing various issues such as the method return the frame pointer of the caller rather than the stack pointer, or the address of a dummy local, for instance. Improve os::current_stack_pointer to work correctly with Link Time Optimization and be more robust to errors, so that it returns the accurate value of the stack pointer, documented below