How to debug a meteor build script

I’ve got an error which causes my build to exit.

After reinstalling various packages, updating stuff and so on, the problem persists.

It’s happening at a line in /tools/isobuild/resolver.js and I would really like to be able to debug this script.
Can anyone give me any pointers as to how to do this?

I’ve found resolver.js in my user’s .meteor folder, although the line numbers don’t seem to match the error message.
At the very least I’d like to be able to log messages about variables to the console output. Can anyone tell me how to do this?

Ok, solved.
I managed to find the problem just by using console.log to print out variables.