Explicitly disable wavpack when building SoX (#1462)

`wavpack` is a format not supported/tested in torchaudio.
Leaving the option blank can cause the issue like #1461 in untested environment.

third_party/sox/CMakeLists.txt

@@ -172,6 +172,7 @@ set(SOX_OPTIONS
   --without-sndio
   --without-sunaudio
   --without-waveaudio
+  --without-wavpack
   --without-twolame
   )