junitxml: failure count and include build errors

Currently the failure count is the len(failures), however if there was an error in package main that failure is not included in the count of failures.

Also build errors are not included in the failures.

Start by locating the JUnit XML generation and failure-count handling in the repository, then reproduce results for a package main error and a build error. Done means both kinds of errors are represented as failures and included in the reported failure count.

Written by the indexing model from the issue text.