gcc4x packages shouldn't build in source directory

[Jack Howarth]

   I just noticed that MacPorts is building the FSF gcc
releases within the source tree. The upstream FSF gcc
developers frown upon this as poor technique. All of the
gcc4X packages should be creating a separate build directory,
eg darwin_objdir, outside of the source tree and then
executing both configure and make from within this
build directory.
                  Jack