macos client-only builds fail

Very strange one. CLIENT_ONLY=1 ./make-all.sh fails with:
cat /Users/macos12/xpra/py2app.log
Traceback (most recent call last):
  File "/Users/macos12/xpra/./setup.py", line 2836, in <module>
    main()
  File "/Users/macos12/xpra/./setup.py", line 2832, in main
    setup(**setup_options)
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/setuptools/_distutils/core.py", line 185, in setup
    return run_commands(dist)
           ^^^^^^^^^^^^^^^^^^
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/setuptools/_distutils/core.py", line 201, in run_commands
    dist.run_commands()
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/setuptools/_distutils/dist.py", line 969, in run_commands
    self.run_command(cmd)
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/setuptools/dist.py", line 1234, in run_command
    super().run_command(command)
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/setuptools/_distutils/dist.py", line 988, in run_command
    cmd_obj.run()
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/py2app/build_app.py", line 987, in run
    self._run()
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/py2app/build_app.py", line 1217, in _run
    self.run_normal()
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/py2app/build_app.py", line 1436, in run_normal
    o = __import__(m1, fromlist=[m2])
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macos12/xpra/xpra/server/base.py", line 13, in <module>
    from xpra.server.core import ServerCore
  File "/Users/macos12/xpra/xpra/server/core.py", line 27, in <module>
    from xpra.scripts.server import deadly_signal, clean_session_files, rm_session_dir
  File "/Users/macos12/xpra/xpra/scripts/server.py", line 56, in <module>
    from xpra.util.child_reaper import getChildReaper
  File "/Users/macos12/xpra/xpra/util/child_reaper.py", line 21, in <module>
    GLib = gi_import("GLib")
           ^^^^^^^^^^^^^^^^^
  File "/Users/macos12/xpra/xpra/os_util.py", line 54, in gi_import
    return importlib.import_module(f"gi.repository.{mod}")
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macos12/gtk/inst/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1204, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1176, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1147, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 676, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 573, in module_from_spec
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/gi/importer.py", line 147, in create_module
    dynamic_module = load_overrides(introspection_module)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/gi/overrides/__init__.py", line 112, in load_overrides
    override_mod = importlib.import_module(override_package_name)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macos12/gtk/inst/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/gi/overrides/GLib.py", line 37, in <module>
    from gi import _option as option
  File "/Users/macos12/gtk/inst/lib/python3.11/site-packages/gi/_option.py", line 41, in <module>
    OPTION_CONTEXT_ERROR_QUARK = GLib.quark_to_string(GLib.option_error_quark())
                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^
gi._error.GError: g-invoke-error-quark: Could not locate g_option_error_quark: dlopen(libglib-2.0.0.dylib, 0x0009): tried: 'libglib-2.0.0.dylib' (no such file), '/usr/local/lib/libglib-2.0.0.dylib' (no such file), '/usr/lib/libglib-2.0.0.dylib' (no such file), '/Users/macos12/xpra/libglib-2.0.0.dylib' (no such file) (1)
There aren't any major differences between regular and client-only builds: https://github.com/Xpra-org/xpra/blob/b16a48f6137e08f43fc38b4d96d16d49b3392ed7/packaging/MacOS/make-app.sh#L27
Why would this have any effect on a GLib import!?
Xpra-org / xpra

macos client-only builds fail #4338
