wx: Add WX_MACOS_NON_GUI_APP

[wojtekmach]

We cannot depend on is_packaged_app() check because it is not a perfect way of checking if app is bundled.

It would return true when the app is bundled with a launcher like this:

import AppKit

let task = Process()
task.launchPath = "/Users/wojtek/src/otp/bin/erl"
task.arguments = ["-noshell", "-eval", "wx:new(), timer:sleep(5000), halt()"]
try task.run()
task.waitUntilExit()

It would return false for this launcher, however:

import AppKit

class AppDelegate: NSObject, NSApplicationDelegate {
    func applicationDidFinishLaunching(_ aNotification: Notification) {
        let task = Process()
        task.launchPath = "/Users/wojtek/src/otp/bin/erl"
        task.arguments = ["-noshell", "-eval", "wx:new(), timer:sleep(5000), halt()"]
        try! task.run()
    }
}

let app = NSApplication.shared
let delegate = AppDelegate()
app.delegate = delegate
app.run()

Btw, there has recently been a fix in wx [1] and we'd only be able to take advantage of it when OSXIsGUIApplication returns true (and when wx recognizes our app as properly bundled, see [2]). And so I believe to support variety of scenarios, we need precise control.

[1] wxWidgets/wxWidgets#22508
[2] #6070 (comment)

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[wojtekmach]

This is PR is really only useful for the 2nd approach I mentioned in the PR description, the AppDelegate one, but there are some caveats with that which I have learned since so let's hold off on this change for a moment.

[wojtekmach]

Yeah, as noted in the PR description there is a variety of scenarios for using wx so I believe more precise control is really useful here. We'd appreciate if we could land this PR so we (Livebook Desktop) could stop using our fork. :)

[dgud]

Can this be done without an env variable, i.e. in some cleaner way?

Or is this such a special case that I should just accept it as it is?

[wojtekmach]

I unfortunately couldn't think of a better way of solving this issue, I think we need to override OSXIsGUIApplication but at the same time control what exactly it returns (so we can opt-out of certain behaviour in wx).

Would controlling this with application:put_env instead be an improvement?

[wojtekmach]

@dgud fyi, for Livebook we are also exploring an altogether different way of building Mac apps with OTP described in #6070 (comment) and for that we wouldn't need this patch. I still think the patch is useful though as there are so many different ways of running OTP and wx and so I think it is very helpful to have some flexibility.