Ensure linted bundles exist

[gaearon]

I added validation of built bundles in #11432.

However I actually messed it up, and ESLint wasn't running on any files because of invalid arguments. I fixed that here: 61d35ce#diff-edcddc0e0143d5a5a93d0951fd599794

We should fail the build if the glob patterns it's searching for don't exist.

[misoguy]

Can I work on this if no one else is on it yet? 😄

[misoguy]

I opened a PR regarding this issue. It would be nice if you could take a look @gaearon 😄

[gaearon]

Thank you so much!