the DIALOG_EXPORT_STEP uses a auto saved copy of the current board to
create the step file (using kicad_cli).
But this file is not associated to a corresponding .kicad_pro file, and
this can create some issues (like the KIPRJMOD not defined)
So create a copy of the current board prj to export associated prj file
to the auto saved board file.
From master branch

Fixes #16973