I’ve just tried rebuilding an existing project on macOS, last build a couple of months ago. The debug build runs okay, but the release build hangs with the message above. Web search suggests this is an issue with Mojave, see e.g.: " Apple Event sandboxing in macOS Mojave lacks essential APIs" (https://www.felix-schwarz.org/blog/2018/06/apple-event-sandboxing-in-macos-mojave).
I wonder if there is a known fix to use with JUCE. As a cross platform development it would be nice not to get bogged down in OS specific workarounds if possible…
Running macOS Mojave and JUCE v5.4.1, Xcode 10.1.