解决办法：
需要修改.idea/workspace.xml 在<component name="PropertiesComponent">里添加<property name="dynamic.classpath" value="true" />
<component name="PropertiesComponent">
<property name="last_opened_file_path" value="$PROJECT_DIR$/../acpp-po" />
<property name="dynamic.classpath" value="true" />
</component>