/usr/include/GNUstep/Cynthiune is in cynthiune.app 1.0.0-1build2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/include/GNUstep/../../lib/GNUstep/Frameworks/Cynthiune.framework/Headers
/usr/include/GNUstep/../../lib/GNUstep/Frameworks/Cynthiune.framework/Headers