Xcode build crashes if PlugIns directory is not present

[ann0see]

Describe the bug

The Xcode build of Jamulus after the merge of #3076 crashes with the error message - allocated port number: 22134 qt.qpa.plugin: Could not find the Qt platform plugin "cocoa" in "" This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

To Reproduce

Compile Jamulus with Xcode. To do so run qmake -spec macx-xcode Jamulus.pro
Run the app via Xcode and observe a crash. Running the binary from the command line from the Debug folder gives this error message.

Strange enough, if the I build with qmake Jamulus.pro; make the created binary works as expected but doesn't seem to have a PlugIns directory in Jamulus.app/Contents. If I copy the PlugIns directory from a previous build to the crashing build, everything works.
Expected behavior

Xcode builds don't crash
Screenshots

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Operating system

macOS 13.4; Xcode 14.2
Version of Jamulus

Build form 10c7eaf4a7ecb59c6a79dd65f3bd6bd172e217dd
Additional context

this Mac runs an unsupported version of macOS, so it could be another issue (dortania/OpenCore-Legacy-Patcher#1046) but I doubt that.

[ann0see]

Maybe macdeployqt must be run somehow