Set BUILD_WITH_PYTHON to ON by default in CMakeLists.
Set BUILD_WITH_PYTHON to ON by default in CMakeLists.

Fixes: #299.
PiperOrigin-RevId: 321570756
Change-Id: Id3f562bba678c36b60e4d53aa9c859026389ec6c

deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel