Go: Improve log messages in buildWithoutCustomCommands

[mbg]

Summary

As pointed out in #16469, the log message in buildWithoutCustomCommands that reads "Build failed, continuing to install dependencies" is confusing for users since it doesn't actually mean that we failed to build a project. It just means that we failed to find or run a build script such as a Makefile.

What this PR does

This PR fixes #16469 by:

1. Improving the wording of the log message.
2. Modifying the Autobuild function to also return an array of scripts that were executed.
3. Improving the log messages further by checking the length of that array to see whether any scripts were found or not.

[smowton]

Looks sensible, one style nitpick