Huh, it appears the tests for these features are relying solely on the command line options, and not checking that the environment variables are also setting the flags properly. We should be able to account for that omission with a single new test in `test_cmd_line` that sets every relevant environment variable and checks for the expected `sys.flags` contents.

As far as what's actually going wrong goes, it's this sequence of events in Py_Main:

    _Py_InitializeCore(&core_config);
    ... other code ...
    apply_command_line_and_environment(&cmdline);

_Py_InitializeCore is setting the internal flags appropriately based on the runtime environment, but then Py_Main is stomping over those environmental settings with the settings from the command line.

Historically, these operations happened the other way around, so it was solely up to the code reading the environment variables to ensure they played nice with each other. Now the command line processing logic needs to be updated to also ensure that it only ever increases these values and never reduces them.