自己解决了,全部手写:
COMMAND ${EXTERNAL_QT_DIR}/bin/uic ${CMAKE_CURRENT_SOURCE_DIR}/mainwindow.ui -o ${CMAKE_CURRENT_SOURCE_DIR}/ui_mainwindow.h
COMMAND ${EXTERNAL_QT_DIR}/bin/moc ${CMAKE_CURRENT_SOURCE_DIR}/mainwindow.h -o ${CMAKE_CURRENT_SOURCE_DIR}/moc_mainwindow.cpp
COMMAND ${EXTERNAL_QT_DIR}/bin/rcc ${CMAKE_CURRENT_SOURCE_DIR}/my_resource.qrc -o ${CMAKE_CURRENT_SOURCE_DIR}/qrc_my_resource.cpp