[remux] PATH variable not including opt dirs

[LinusCDE]

An app failed to start in a merge review: https://github.com/toltec-dev/toltec/pull/619#pullrequestreview-1079706773

The issue was that is was expecting /opt/bin to be in $PATH but apparently wasn't. The path variable available to remux should probably be made available to programs started by it as well.

For I added a patch for the affected package (https://github.com/toltec-dev/toltec/pull/620).