Build .app for macOS in Linux environment

[tpimh]

Description

Currently, it's only possible to build for macOS using act with -P macos-latest=-self-hosted. This limitation comes from plutil not being available on Linux.

I have found a cross-platform, drop-in replacement for plutil. The downside: no binaries available, needs to be compiled from source.

So I just added these compilation steps to the script that sets up the environment. They are running conditionally, only when building on Linux for macOS and plutil is not found in PATH.

Now it can be tested by running act -P macos-latest=catthehacker/ubuntu:act-22.04. Alternatively, you can specify your own Docker image with plutil binary included, this would allow to skip the compilation and speed up the whole process.

The resulting package needs to be compared against similar created with -self-hosted option, and if there are no significant differences, this can be merged.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• I have performed a self-review of my code
• I have tested my code in common scenarios and confirmed there are no regressions