Summary:
Update the thrift C++ and Python CMake rules to indicate that the output also
depends on the thrift compiler itself.

Previously the C++ rule indicated that the output depended on the thrift
template files, which caught most cases when the thrift compiler was updated,
but wasn't fully correct.  The thrift templates were also removed and baked
into the thrift compiler binary in D16356056.

Reviewed By: yfeldblum, chadaustin

Differential Revision: D17401217

fbshipit-source-id: ae5cde7a7e5e07a74406a1b6f4469124187bc12f