The command used for building the packages is
fakeroot dpkg-buildpackage > ../build_log_r-base_i386 2> ../build_errors_r-base_i386

and for the amd64 build
fakeroot dpkg-buildpackage -B > ../build_log_r-base_amd64 2> ../build_errors_r-base_amd64

Didn't figure out how to do this with tee yet...