gnulib-tool.py: Bring the output into the right order. * pygnulib/constants.py (force_output): New function. (execute): Flush stdout after printing the "executing ..." line. * pygnulib/GLTestDir.py (GLTestDir.execute, GLMegaTestDir.execute): Invoke force_output. * pygnulib/main.py (test, megatest): Likewise.