virtualenv is not able to detect free-threading python3.13t

[ssbarnea]

Issue

The free-threading python 3.13 has a new executable python3.13t and virtualenv is unable to detect it.

Environment

Any

Output of the virtual environment creation

Make sure to run the creation with -vvv --with-traceback:

$ virtualenv -p 3.13t
RuntimeError: failed to find interpreter for Builtin discover of python_spec='3.13t'
FAIL: 1


$ virtualenv -p 3.13
usage: virtualenv [--version] [--with-traceback] [-v | -q] [--read-only-app-data] [--app-data APP_DATA] [--reset-app-data] [--upgrade-embed-wheels] [--discovery {builtin}] [-p py] [--try-first-with py_exe]
                  [--creator {builtin,cpython3-posix,venv}] [--seeder {app-data,pip}] [--no-seed] [--activators comma_sep_list] [--clear] [--no-vcs-ignore] [--system-site-packages] [--symlinks | --copies] [--no-download | --download]
                  [--extra-search-dir d [d ...]] [--pip version] [--setuptools version] [--wheel version] [--no-pip] [--no-setuptools] [--no-wheel] [--no-periodic-update] [--symlink-app-data] [--prompt prompt] [-h]
                  dest
virtualenv: error: the following arguments are required: dest
SystemExit: 2
FAIL: 2