`dart pub global activate` should error if there are build hooks

[dcharkes]

Since dart pub <...> is implemented in this package, we need to do that here.

If we don't want to duplicate code between dartdev and pub for checking whether there are hooks, we should consider adding a callback function to

Command<int> pubCommand({required bool Function() isVerbose}) =>
    PubEmbeddableCommand(isVerbose);

[sigurdm]

How do you check if you have a hook?

[sigurdm]

If the check is simple, I'd rather re-implement to simplify testing outside the scope of the sdk

[dcharkes]

How do you check if you have a hook?

Look at all the packages that are a transitive dependency of the root package (via the dependencies graph), and check whether the file hook/build.dart exists. (It's important to take the root package into account, otherwise other packages with hooks in the workspace cause false positives.)