Add reference to https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++

[kbeyls]

[kbeyls]

https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++ is a great document with great recommendations for C and C++ compiler security features people should consider using by default. We should have a paragraph on it and refer to it from the book.

It seems most recommended hardening features relate to protecting against memory vulnerabilities, so maybe adding it to the chapter about memory vulnerabilities makes most sense?