Show compile-time error/warning for using `@angular/compiler` with optimized builds

Start by tracing the Angular CLI build path for optimized builds and how it handles user imports of @angular/compiler. Define completion as detecting that combination during the build and reporting a precise warning or error that explains the JIT/build-optimizer incompatibility and the available fix.

🚀 Feature request

Command (mark with an x)

• build

Description

Currently it is possible to have a configuration which uses AOT compilations but also JIT during runtime and attempts to run build optimizer on the results. This doesn't really work and isn't supported, leading to awkward error messages, which can be confusing to users (see #17663).

Describe the solution you'd like

Ideally, the CLI would detect this case and error out if an import for @angular/compiler is found in user code with build optimizer enabled. We should display a more precise warning/error about this case to better explain to the users why JIT + build optimizer doesn't work and what they can to do fix it.

Describe alternatives you've considered

Currently this is a runtime error with a poor message.

main.7000374ef126bad8069c.js:1 ERROR Error: Uncaught (in promise): Error: Angular JIT compilation failed: '@angular/compiler' not loaded!
  - JIT compilation is discouraged for production use-cases! Consider AOT mode instead.
  - Did you bootstrap using '@angular/platform-browser-dynamic' or '@angular/platform-server'?
  - Alternatively provide the compiler with 'import "@angular/compiler";' before bootstrapping.
Error: Angular JIT compilation failed: '@angular/compiler' not loaded!
  - JIT compilation is discouraged for production use-cases! Consider AOT mode instead.
  - Did you bootstrap using '@angular/platform-browser-dynamic' or '@angular/platform-server'?
  - Alternatively provide the compiler with 'import "@angular/compiler";' before bootstrapping.
    at Ae (main.7000374ef126bad8069c.js:1)
    at Function.get (main.7000374ef126bad8069c.js:1)
    at St (main.7000374ef126bad8069c.js:1)
    at new Af (main.7000374ef126bad8069c.js:1)
    at ud (main.7000374ef126bad8069c.js:1)
    at dd (main.7000374ef126bad8069c.js:1)
    at e.md [as compileModuleAndAllComponentsAsync] (main.7000374ef126bad8069c.js:1)
    at e. (main.7000374ef126bad8069c.js:1)
    at Generator.next ()
    at main.7000374ef126bad8069c.js:1
    at T (polyfills.a8d522dff2c1a5c4b9db.js:1)
    at polyfills.a8d522dff2c1a5c4b9db.js:1
    at a (main.7000374ef126bad8069c.js:1)
    at l.invoke (polyfills.a8d522dff2c1a5c4b9db.js:1)
    at Object.onInvoke (main.7000374ef126bad8069c.js:1)
    at l.invoke (polyfills.a8d522dff2c1a5c4b9db.js:1)
    at i.run (polyfills.a8d522dff2c1a5c4b9db.js:1)
    at polyfills.a8d522dff2c1a5c4b9db.js:1
    at l.invokeTask (polyfills.a8d522dff2c1a5c4b9db.js:1)
    at Object.onInvokeTask (main.7000374ef126bad8069c.js:1)