Simon ‘corecode’ Schubert has updated gcc to version 4.0.1.
If you want to build the system using gcc version 4, you must put WANT_GCC40=yes into make.conf and rebuild your system. Then, rebuild again with the environment variable CCVER set to ‘gcc40’.
The first build builds gcc4 using your existing compiler; the second uses it during the build. I have not done this myself, so be careful.