Enables tracing output for target properties.

This variable can be populated with a list of properties to generate debug output for when evaluating target properties. Currently it can only be used when evaluating the INCLUDE_DIRECTORIES, COMPILE_DEFINITIONS, COMPILE_OPTIONS, AUTOUIC_OPTIONS, SOURCES, COMPILE_FEATURES, POSITION_INDEPENDENT_CODE target properties and any other property listed in COMPATIBLE_INTERFACE_STRING and other COMPATIBLE_INTERFACE_ properties. It outputs an origin for each entry in the target property. Default is unset.