Check the requirements after installing "requires_for_build_wheel"
    
    If not checked, installing runtime requirements might fail.
    
    When a requirement is specified in setuptools' setup_requires:
    
        setup(
            ...
            setup_requires=["pytest-runner"],
        )
    
    It is part of the get_requires_for_build_wheel hook output.
    
    When runtime requirements are parsed with setuptools without all setup_requires
    present, it tries to get them from the internet (at least on Fedora 33).
    
    By checking the requirements after installing "requires_for_build_wheel",
    we make sure all setup_requires are already installed.
    
    When runtime requirements are not installed, this adds an unneeded check,
    but the script would end at that point anyway, so there is no real difference.