private Path getRelativeToProjectRoot(Path configuration, String propertyName) {
    String property = System.getProperty(propertyName);
    Path path = property != null ? Paths.get(property) : configuration;
    return path.isAbsolute() ? path : project.getProjectDir().toPath().resolve(path);
  }
Object that configures where Jib should create its build output files.
jib-gradle-plugin/src/main/java/com/google/cloud/tools/jib/gradle/OutputPathsParameters.java