rm2fb flag not modifying rpath

[Eeems]

Describe the issue
While we patchelf to add the rm2fb dependency, the hook doesn't modify the rpath to allow it to look up the library in /opt/lib. This means that the application will fail with the following error when running it directly:

error while loading shared libraries: librm2fb_client.so.1: cannot open shared object file: No such file or directory

To resolve this, we should also add /opt/lib to the rpath. Currently all packages that use the rm2fb flag are affected.