config: try harder at finding the configuration
config: try harder at finding the configuration

In Go <1.13, generated files didn't happen to be at the front of the
list of files. In Go 1.13 they do, so we have to stop being lazy. Find
the first file that looks like it isn't in the build cache.

dominikh/go-tools,dominikh/go-tools,dominikh/go-tools,dominikh/go-tools