private Path getRelativeToProjectRoot(Path configuration, String propertyName) {
    String property = getProperty(propertyName);
    Path path = property != null ? Paths.get(property) : configuration;
    return path.isAbsolute() ? path : getProject().getBasedir().toPath().resolve(path);
  }
Gets the configured extra layer file permissions.

@return the configured extra layer file permissions
jib-maven-plugin/src/main/java/com/google/cloud/tools/jib/maven/JibPluginConfiguration.java