qtimageformats breaks top-level build

$ ../qt6/configure -developer-build -debug -no-optimize-debug -no-tslib -no-pch -nomake examples
...
CMake Error at /home/rutledge/dev/qt6-dbg/qtbase/lib/cmake/Qt6Core/Qt6CoreMacros.cmake:2498 (add_library):
  Cannot find source file:

    LIBRARIES
Call Stack (most recent call first):
  /home/rutledge/dev/qt6-dbg/qtbase/lib/cmake/Qt6Core/Qt6CoreMacros.cmake:2331 (_qt_internal_add_library)
  qtbase/cmake/QtPluginHelpers.cmake:87 (qt6_add_plugin)
  qtimageformats/src/plugins/imageformats/jp2/CMakeLists.txt:7 (qt_internal_add_plugin)

# Generated from jp2.pro.

#####################################################################
## QJp2Plugin Plugin:
#####################################################################

qt_internal_add_plugin(QJp2Plugin
    OUTPUT_NAME qjp2
    PLUGIN_TYPE imageformats
    SOURCES
        main.cpp
        qjp2handler.cpp qjp2handler_p.h
    LIBRARIES
        WrapJasper::WrapJasper
    LIBRARIES
        Qt::Core
        Qt::Gui
)

#### Keys ignored in scope 1:.:.:jp2.pro:<TRUE>:
# OTHER_FILES = "jp2.json"
# QT_FOR_CONFIG = "imageformats-private"