Follow-up fix policy set (#3046)

Summary:
Commit b4c66d1f broke all the CIs.
The new policy changes the timestamp of configuration files of third party libraries,
which triggers re-configuration which requires extra tools.

This commit fixes it by reverting the old behavior.
Also this adds guard for older cmake versions.

Pull Request resolved: https://github.com/pytorch/audio/pull/3046

Reviewed By: atalman

Differential Revision: D43133536

Pulled By: mthrok

fbshipit-source-id: 357055c8c1b53e593b8b7880f2045e13512c7a8f

CMakeLists.txt

@@ -17,7 +17,9 @@ if(NOT CMAKE_VERSION VERSION_LESS 3.15.0)
 endif()
 
 # Suppress warning about ExternalProject_Add timestamp
-cmake_policy(SET CMP0135 NEW)
+if(NOT CMAKE_VERSION VERSION_LESS 3.24.0)
+  cmake_policy(SET CMP0135 OLD)
+endif()
 
 project(torchaudio)