enable to use some hardening flags
enable to use some hardening flags

- Maybe CC is not only gcc (e.g. clang)
- add $(CPPFLAGS) and $(LDFLAGS) for hardening
- at least -O3 is not best for default variable, -O2 is better
- sometimes debug information is necessary

martylamb/nailgun,martylamb/nailgun,martylamb/nailgun