Adding web worker via "ng generate webWorker" does not generate differential builds

[joshcomley]

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• xi18n
• run
• config
• help
• version
• doc

Is this a regression?

Unsure, I've only just encountered a scenario that would reveal this bug.

Description

Differential builds are not generated for web workers, only es2015.

🔬 Minimal Reproduction

• Step 1
  ng new NgWorkerDiffTest --routing=false --style=scss & cd NgWorkerDiffTest & ng generate webWorker MyWorker
• Step 2
  Modify app.component.ts to include:

    if (typeof Worker !== "undefined") {
      const worker = new Worker("./my-worker.worker", { type: "module" });
    }

• Step 3
  ng build or ng build --prod - neither will produce anything but es2015 for the worker.

🌍 Your Environment

Angular CLI: 9.0.0-rc.3
Node: 12.12.0
OS: win32 x64
Angular:
...

Package                      Version
------------------------------------------------------
@angular-devkit/architect    0.900.0-rc.3
@angular-devkit/core         9.0.0-rc.3
@angular-devkit/schematics   9.0.0-rc.3
@schematics/angular          9.0.0-rc.3
@schematics/update           0.900.0-rc.3
rxjs                         6.5.3

Anything else relevant?

In a way - IE11 will fail to load workers due to syntax errors.

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