Re-add generate_latest_map script
Re-add generate_latest_map script

It was removed from the build-tools repository. Add it to extra/ and fix
a couple of linter errors.

weaveworks/scope,paulbellamy/scope,paulbellamy/scope,paulbellamy/scope,alban/scope,weaveworks/scope,alban/scope,kinvolk/scope,weaveworks/scope,paulbellamy/scope,weaveworks/scope,kinvolk/scope,kinvolk/scope,paulbellamy/scope,alban/scope,paulbellamy/scope,alban/scope,alban/scope,kinvolk/scope,weaveworks/scope,kinvolk/scope,kinvolk/scope,alban/scope,weaveworks/scope