The gen_header.py script is failing for older versions of python3 such
as python 3.5. Two issues observed with python 3.5 are ...
1. Python 3 versions prior to 3.6 do not support the f-string format.
2. Early python 3 versions do not support the 'required' argument for
the argparse add_subparsers().
Fix both of the above so that older versions of python 3 still work.
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28780>