Wrong lookup of "Env" module

[mshinwell]

Set breakpoint on Flambda_to_clambda.to_clambda
Look at the "env" argument. The value has six fields but the extracted type has 14. Six is correct for Flambda_to_clambda.Env.t. It looks like it's found the Env.t from typing/env.ml instead, which is wrong. This may be something to do with the fact that the Env module is a submodule of Flambda_to_clambda.