docs: private static Class<?> loadVirtualMachine(File toolsJarFile) throws Exception {
          // We used to add tools.jar to SystemClassLoader but that was triggering
          // a bug in Java compiler when running some experiments (e.g.,
          // CommonsMath).
          if (toolsJarFile == null) {
              return null;
          }
          URLClassLoader loader = new URLClassLoader(new URL[] { toolsJarFile.toURI().toURL() },
                  ClassLoader.getSystemClassLoader());
          return loader.loadClass("com.sun.tools.attach.VirtualMachine");
      }