/usr/share/gir-1.0/JSCore-3.0.gir is in libjavascriptcoregtk-3.0-dev 2.4.9-1~deb8u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/gir-1.0/JavaScriptCore-3.0.gir
/usr/share/gir-1.0/JavaScriptCore-3.0.gir