Reintegrates changes from cf9fc84669

This fixes an issue where the app icon would not be visible for
standalone plugin targets.

In order to display a WebKit based webview a plugin will deploy a
temporary standalone executable on the system and host the WebKit
instance inside that.

JUCE no longer depends on built artifacts of the AAX_SDK

This issue made hosts not recognize the ARA capabilities of AU plugins.

Some hosts on Apple Silicon require that the entire bundle has a
well-formed signature, rather than just the plugin binary itself. This
patch checks whether the bundle signature is valid, and if it is not,
ad-hoc signs the bundle before copying.

This build mode does not include support for juceaide or the
juce_add_* suite of helper functions.