Early articles may have problems running lit

[j2kun]

If you're following along PR by PR and checking out individual commits to run examples, you may encounter python complaining it can't find the lit module.

In the fourth article in the series I realized bazel was using the system Python, and https://github.com/j2kun/mlir-tutorial/commit/aac84908f7b09ec1b14489bbc0837e697b191630 migrates to a bazel-managed python runtime.

A simple fix is to run pip install lit in your system Python. Or else cherry pick aac84908f7b09ec1b14489bbc0837e697b191630 to your step in the article series.