A package to be uploaded to the Debian repositories should avoid /opt and /usr/local - these directories are reserved for the local system administrator, as per the Filesystem Hierarchy Standard. The lintian tags reflect this. You should, instead, structure your package so that:
- executables go in
/usr/bin (or /usr/sbin, as the case maybe)
- libraries go in
/usr/lib or an appropriate subfolder thereof
- architecture-independent shared data in a subfolder in
/usr/share, etc.
Consult the Debian Policy for more information.
If your package is for local use, you can go ahead and ignore that tag. You can create a lintian override to stop lintian from generating that error.