Android app does not build due to unknown properties.

Executing gradle on the repo results in the following error.

Build file '/home/baldo/projects/luca/android/Luca/app/build.gradle' line: 16

A problem occurred evaluating project ':app'.
> Could not get unknown property 'C4L_SIGNING_KEY_ALIAS' for project ':app' of type org.gradle.api.Project.

Edited Apr 03, 2021 by baldo