Reproducing a builder's build can generally be done by following the instructions located under the 'run_recipe' link on the build page itself.
In particular, you need to install depot_tools, and then get a build checkout:
$ cd <empty dir>
$ # One of:
$ fetch infra # external user
$ fetch infra_internal # internal user
$ cd build
And then navigate to a build that you want to repo. Look for the build step which looks like:
If you don't see a setup_build step, then you'll have to run a local master and slave, as documented here.