/usr/lib/libfeelpp_gflags.so is in libfeel++-dev 1:0.99.0-final.1-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libfeelpp_gflags.so.2.1.0
/usr/lib/libfeelpp_gflags.so.2.1.0