Dashboard does not correctly link to test source for tests with generated files

[oliverdunk]

For example, see this page: https://wpt.fyi/results/web-extensions/browser.alarms.extension.html?label=master&label=experimental&aligned&q=web-extensions

Clicking either of the "View source on GitHub" links takes you to browser.alarms.extension.html, but this file does not exist as the test source lives in a JS file.

This is also the case for web tests so is not specific to the web-extensions folder.