• The core target was exported with another name of supernovas, causing the CMAke package config to fail, since it was expecting a supernovas::core target, but instead got supernovas::supernovas. Fixed by exporting core without renaming.

Also:

• Removed unnecessary POSITION_INDEPENDENT_CODE from CMakeLists.txt. (It's automatic for shared libraries.)

• Removed CLEAN_DIRECT_OUTPUT from CMakeLists.txt. It's an option that is no longer needed or used (since 2009).

• Updated README.md instructions for using supernovas CMake package.