Given that changes to either the Babel plugin or the "old" builder could accidentally cause issues in the built files, it seems like a good idea to run all test-suites when the `external/builder/` folder is changed.
Note that for the integration tests the coverage information ends up
being processed in the Node.js context where `window` is not available,
so we use `globalThis` instead for the function that merges individual
test's coverage information into the global object because that is
available in all contexts we support. For clarity we also rename said
function since we're not exclusively dealing with `window` nor worker
data anymore.
