Hm, that is a problem indeed. The goal is always for the user CFLAGS to
override the automatic CFLAGS. I'm going to fix that.
Actually, things are working as intended. The contents of the CPPFLAGS,
CFLAGS and LDFLAGS *environment variables* do not override the defaults
in the Makefile. However, when CPPFLAGS/CFLAGS/LDFLAGS is used as a
*make variable* ("make CFLAGS=-fstack-protector=yes"), then it does
override the defaults.
If you want the environment variables to also override the defaults,
you can run "make -e".
I should still modify the Makefile to make it easier to override
CFLAGS and friends without having to manually redefine the -I and -L