Fixes #1678: Optimize Bazel protobuf rules install [BLOCKED: #1634]

[miaboloix]

Explanation

Fixes #1678: Optimize Bazel protobuf rules install.

Currently, http_rules in WORKSPACE are used to import rules_java and rules_proto, the external dependencies needed to run proto rules like proto_library and java_lite_proto_library in Bazel.

However, these http_archive rules bring in more than what is needed to use proto_library and java_lite_proto_library and some of these unused artifacts come with lengthly and expensive download times.

Thanks to @anandwana001, the following solution was found: https://github.com/google/startup-os/blob/master/WORKSPACE#L173. By replacing the http_archive rules with these bindings and removing the now unnecessary load() statements from model/BUILD, we are able to import only what is necessary.

Building app library from clean...

• Before optimization: ~3min 45s
• After optimization: ~2min 55s

Checklist

• The PR title starts with "Fix #bugnum: ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
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[BenHenning]

Following back up. Fantastic build time improvement! I still want to better understand whether this is the correct approach & why, and ensure that's documented before we go ahead with the solution.

[BenHenning]

Thanks @miaboloix!