Search for the 32blit executable if the module fails

[Daft-Freak]

Recently, trying to pip install 32blit results in:

error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
    python3-xyz, where xyz is the package you are trying to
    install.

    If you wish to install a non-Debian-packaged Python package,
    create a virtual environment using python3 -m venv path/to/venv.
    Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
    sure you have python3-full installed.

    If you wish to install a non-Debian packaged Python application,
    it may be easiest to use pipx install xyz, which will manage a
    virtual environment for you. Make sure you have pipx installed.

    See /usr/share/doc/python3.11/README.venv for more information.

note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.

(or replace Debian/apt with Arch/pacman, or whatever else you're using...)

Okay, there aren't any 32blit-tools packages so let's try pipx install 32blit:

  installed package 32blit 0.7.3, installed using Python 3.11.3
  These apps are now globally available
    - 32blit
done! ✨ 🌟 ✨

Now I can run 32blit and do things... except build, as that uses python3 -m ttblit which isn't found because I'm not running VS code in the venv (unless I set PYTHON_EXECUTABLE to point to the right thing)

So this PR is fixing that with a find_program and some find/replace.