/usr/lib/libsidlstub_cxx.so is in libsidl-dev 1.4.0.dfsg-8build3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libsidlstub_cxx-1.4.0.so
/usr/lib/libsidlstub_cxx-1.4.0.so