containertool should warn if the user attempts to stack a mach-O executable on top of a Linux base image #132
Description
When using containertool directly, or if accidentally using the plugin without a --swift-sdk, it is possible to end up layering a mach-O (macOS) executable on top of a Linux container image. This will not run, but the error messages which are printed when trying to run such an image can be difficult to understand.
containertool already tries to read an ELF header from the executable, in order to choose the correct base image architecture. It could also detect that the executable is a mach-O binary and warn the user.