where to put NO_MKTIME_BEFORE_1970?

I'm running Red Hat 7.3 at home. For the fun of it, I put:  #define NO_MKTIME_BEFORE_1970

into /src/include/port/linux.h and then did:
make clean
make all
make install
initdb
make installcheck

But I'm still getting the < 1970 regression test failures. What else do 
I need to do?

Joe