Autobuild: Combine scripts into single script per-platform

[hoffie]

What is the current behaviour and why should it be changed?

• The autobuild scripts have grown a lot and are hard to reason about.
• Code is duplicated within the same platform (GITHUB_WORKSPACE handling), across platforms (e.g. mac & ios are very similar, yet they are copies).
• They rely on the discouraged, insecure Github feature ACTIONS_ALLOW_UNSECURE_COMMANDS: 'true' (which could be worked around, but why do that if we can make it redundant?)

Describe possible approaches

My plan is to combine all the platform-specific scripts into a single per-platform script.

• Autobuild: Combine and simplify Windows build scripts #2502
• Autobuild: Combine and simplify Linux build scripts #2509
• Autobuild: Combine and simplify Mac build scripts #2514
• Autobuild: Combine and simplify iOS build scripts #2521
• Autobuild: Combine and simplify Android build scripts #2527
• Autobuild: Derive all step commands from a base_command + multiple minor fixes #2540
• Check if Mac/iOS can partially re-use stuff from the other script: After looking at the diff, it's not worth it
• Mac/iOS: Shorten artifact_deploy_filename
• Mac: Simplify PATH handling similar to iOS
• Convert autobuild.yml to use a single command: in the build matrix & adjust inline comments
• Consider moving the scripts to .github/autobuild/ instead (see Autobuild: Combine and simplify Windows build scripts #2502 (comment))
• Remove unused Workflow environment variables (e.g. jamulus_project_path)
• Consider moving the autobuild-only scripts from .github/action_scripts to .github/autobuild/ or .github/autobuild_scripts (@ann0see) as well, contained in Autobuild: Clean up redundant variables in workflow definition #2584 and Autobuild: Improve and reorganize git/Changelog scripts (re-submission of #2584) #2656
• Consider removing deploy/ from autobuild.yml to allow scripts to set output directly instead of copying stuff around: This isn't possible as the name is used both for the path (that's fine) and the name (that's problematic as it should not be a path, obviously).
• Remove ensure_THIS_JAMULUS_PROJECT_PATH.sh
• "Install dependencies" -> "Install Qt"
• Linux: Use 'Jamulus Development Team <team@jamulus.io>' #2652
• #!/bin/bash & set -eu everywhere?
• powershell ".\windows\deploy_windows.ps1" "C:\Qt\${Qt32Version}" "C:\Qt\${Qt64Version}" @ExtraArgs
• export DEBIAN_FRONTEND="noninteractive" everywhere?
• dch --create --package jamulus --empty --newversion "${VERSION}" '' -> use jamulus_buildversionstring doesn't make sense as it has to match Jamulus.pro for dev builds
• jamulus_buildversionstring -> JAMULUS_BUILD_VERSION?

Has this feature been discussed and generally agreed?

Previous announcement: #2282 (reply in thread)

[ann0see]

In a perfect setup I'd like the following:

.github/autobuild :

windows/linux/... scripts set up the environment

The autobuild script calls a build script - which could also be run locally, which

1. Builds and packages Jamulus
2. Moves the files to deploy/