Swift_MODULE_DIRECTORY
----------------------

Specify output directory for Swift modules provided by the target.

If the target contains Swift source files, this specifies the directory in which
the modules will be placed.  When this property is not set, the modules will be
placed in the build directory corresponding to the target's source directory.
If the variable :variable:`CMAKE_Swift_MODULE_DIRECTORY` is set when a target is
created its value is used to initialise this property.
