Revamp ScanCode installation packages

[pombredanne]

We have several pesky installation issues that come up on certain new or different OS/arch/Python combos. This makes the initial experience really poor for some users.

We need to rethink the entire OS support and installation approach

The key is likely to always include a Python interpreter and to build installers as described in #1703

• an AppImage for Linux
• some Windows installer (wix, NSIS?) for Windows (or use only a WSL2 AppImage? See RFC: Drop native Windows support for WSL2 #2366 )
• an mpkg for macOS

With this we would limit the set of app archive we would create to one for each OS/arch combo.

The other usages should be developer type use that work from sources and a checkout.

[Jeeppler]

An AppImage for Linux Desktop users is a good idea. Download it and run it.

However, the drawback is that one has to download the app and run it, like on Windows. Meaning, there is no repository which one can just search and install Scancode from. There is also no possibility to get updates automatically.

To support a variety of use cases it would be best to package Scancode for Debian, Alpine, Fedora, Rocky Linux, Guix and other distributions. This would allow to cover use cases such as running Scancode on different devices, virtual machines, containers and many more.

For example, let's assume Scancode is packaged for Debian. It will then be available in the Debian distribution as well as it's derivatives over time. Derivatives like Ubuntu, Linux Mint, Devuan and many others.
Additionally, Debian supports a number of different instruction set architectures.

[sschuberth]

I'd like to chime in here by saying that I'm having a hard time to get https://github.com/nexB/scancode-toolkit/releases/download/v31.2.1/scancode-toolkit-v31.2.1_py3.8-linux.tar.gz to run on Fedora 36 (KDE Spin).

The first problem is that the release archive comes with a PYTHON_EXECUTABLE file that contains the string python3.8, so the configure script sets that as the interpreter, but on Fedora I have Python 3.10.8, so it fails with the minor version hard-coded to "8". However, that can be easily worked around by deleting the PYTHON_EXECUTABLE file before running ScanCode for the first time, which makes the configure script fall back to python3 as the interpreter.

Then, the next problem is

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [3 lines of output]
      Building lxml version 4.9.1.
      Building without Cython.
      Error: Please make sure the libxml2 and libxslt development packages are installed.
      [end of output]

However, I have

Package libxml2-2.10.3-2.fc36.x86_64 is already installed.
Package libxslt-1.1.37-1.fc36.x86_64 is already installed.

Any hints how to resolve this?