This plugin must be built inside gerrit source tree with bazel.
$ git clone https://gerrit.googlesource.com/gerrit $ cd gerrit $ git clone https://.... plugins/supermanifest
rm plugins/external_plugin_deps.bzl ln -s supermanifest/external_plugin_deps.bzl plugins/external_plugin_deps.bzl
$ bazel build //plugins/supermanifest:supermanifest