GCC expects __stack_chk_fail() to be noreturn[1].  Returning from
__stack_chk_fail() can thus lead to subtle failures.

When crashing, use a volatile NULL pointer dereference.  Ideally we
would like to "abort()" here, but doing so would require two more
syscall definitions just for a cold function.  After all, the function
isn't even used at all if -fno-stack-protector is specified.

Also, don't say "stack smashing" (unlike glibc).  The preloader
currently initializes the stack canary value to a fixed value (0), which
serves little value in protecting against actual buffer overrun attacks.

[1]: https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gccint/Stack-Smashing-Protection.html