[Bug middle-end/121222] add support for -fsanitize-coverage=stack-depth

[kees at outflux dot net via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121222

--- Comment #6 from Kees Cook <kees at outflux dot net> ---
The primary difference is the compile-time guard for instrumentation that
depends on stack usage.