Add a few extra hardening CXXFLAGS

[basicallygit]

Adds some extra hardening compiler flags, most of them also commonly used in chromium

-fno-delete-null-pointer-checks: Make sure the compiler does not optimize away null pointer checks

-ftrivial-auto-var-init=zero: Automatically initialize uninitialized auto variables to zero

-Og -D_FORTIFY_SOURCE=2: Add bounds checking to insecure string handling functions, -Og is the minimum required optimization set to enable FORTIFY_SOURCE, and also helps with debugging. -O2 would be nicer but probably negatively affects debugging

-Wl,-z,relro -Wl,-z,now: Enable Full RELRO support

-Wl,-z,noexecstack: Mark stack as non-executable

adding -fPIE -pie to the executables to take full advantage of ASLR would also be nice however im not good enough at makefile for that. The .so objects already use full ASLR with -fPIC so those are fine