executables never have "USE_TIMINGOUTPUT"
this comes from updates/cleanups to/of the CMake setup.
Problem: even though turtle is built/installed with the timing option turned on, executables never know about it.
This is because the "USE_TIMING" setting never gets defined in the _code.py
-generated temporary cmake setup that's being used for the executables.
Current workaround: always define USE_TIMINGOUTPUT
for the executable.
We need a reasonable solution.