The rearranged code should do exactly what the old code did, but
the new code avoids a potentially costly re computation in the case
where a boundary already exists.

Issue #10188 (partial resolution): tidy up some behaviour in the new tempfile.TemporaryDirectory context manager

instead of bininstall target so it shows up when you do 'make altinstall'.
Closes issue 10677.

This makes the output of the function and those that depend on it
independent of whether or not they are being run under a debug
build.