Reports aren't able to read base64 source maps files
Looking at this line here: https://github.com/bcoe/c8/blob/master/lib/report.js#L189
It's not able to read files which have their content encoded as a base64 path.
Example: path/to/file:application/json;base64,{base64 content}

Right now it'll throw an error like:

ENAMETOOLONG: name too long, open path/to/file:application/json;base64,{base64 content}