[monorepo] split out build-only web engine into its own builder

[yjbanov]

Fixes flutter/flutter#160211

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[jtmcdole]

This and some ET problems?

00:00 �[32m+0�[0m�[31m -1�[0m: test smoke test -- this test SHOULD FAIL �[1m�[31m[E]�[0m�[0m

  Expected: true
    Actual: <false>


  Expected: true
    Actual: <false>

Invalid argument (name): Expected to start with a valid platform name (i.e. linux/) or "ci/": "web_build/artifacts"
#0      mangleConfigName (package:engine_tool/src/build_utils.dart:57:3)

[eyebrowsoffire]

I'm confused by this change. Does this mean we are going to actually build all the artifacts twice in every presubmit?

[yjbanov]

@eyebrowsoffire

I'm confused by this change. Does this mean we are going to actually build all the artifacts twice in every presubmit?

Unfortunately for now, yes. The good news is that it shouldn't be too much overhead. Currently, linux_web_engine performs the following work:

• Build:
  • The engine build itself - 13 min (but due to drone overhead it currently costs 20 min).
  • Engine tests - 8 x 7 min = 56 min
• Test:
  • Chrome: 2 x 25 min = 50 min
  • Safari: 12 min
  • Firefox: 12 min

So that's 20 + 56 + 50 + 12 + 12 = 150 min worth of work total.

The new linux_web_engine_build builder duplicates just the 13 min (we don't need drones, so there's no extra 7 min overhead), and it moves the artifact upload work to itself so there's no duplication there.

So overall, I do not expect more than 15% overhead total. However, it will remove massive amounts of overhead from the merge queue by reducing the amount of work from 150 min to something <20min.