As it turns out, this was not so easy fix. I had to do:
- add at least c++0x support to scons (works for g++ 4.4.7!)
- change how my DefineVariables works

The c++0x support is bonus, since now we can use some additional features, like auto keyword (see https://gcc.gnu.org/gcc-4.4/cxx0x_status.html).