private static void setPropertySafe(String property, @Nullable String value) {
    if (value != null) {
      System.setProperty(property, value);
    }
  }
Set proxy system properties based on Maven proxy configuration.

@param proxy Maven proxy settings
jib-maven-plugin/src/main/java/com/google/cloud/tools/jib/maven/MavenSettingsProxyProvider.java