Per-configuration output directory for RUNTIME target files.

This is a per-configuration version of the RUNTIME_OUTPUT_DIRECTORY target property, but multi-configuration generators (VS, Xcode) do NOT append a per-configuration subdirectory to the specified directory. This property is initialized by the value of the CMAKE_RUNTIME_OUTPUT_DIRECTORY_<CONFIG> variable if it is set when a target is created.

Contents of RUNTIME_OUTPUT_DIRECTORY_<CONFIG> may use generator expressions.