message: speed up mvfst build by not building fizz test target
  Summary:
  When consuming fizz as an external target, it's wasteful to build test targets
  of fizz.
  This should fix the travis build timeout of mvfst in oss:
diff: @@ -10,6 +10,7 @@ list(APPEND PREFIX_PATH ${CMAKE_PREFIX_PATH} ${CMAKE_INSTALL_PREFIX})
  list(APPEND CMAKE_ARGS
  -DCMAKE_BUILD_TYPE:STRING=RelWithDebInfo
  -DCMAKE_PREFIX_PATH:STRING=${PREFIX_PATH}
  + -DBUILD_TESTS:STRING=OFF
  )
  if(UNIX AND APPLE)
  list(APPEND CMAKE_ARGS
  