fix(@ngtools/webpack): update supported compiler-cli supported version

`@ngtools/webpack` only supports compiler version 8 as per the peerDependency.

The fixes the `isSupported` version static and also removes code that was to support prior versions of compiler-cli

Author: Alan Agius

packages/ngtools/webpack/src/angular_compiler_plugin.ts

@@ -151,7 +151,7 @@ export class AngularCompilerPlugin {
   }
 
   static isSupported() {
-    return VERSION && parseInt(VERSION.major) >= 5;
+    return VERSION && parseInt(VERSION.major) >= 8;
   }
 
   private _setupOptions(options: AngularCompilerPluginOptions) {
@@ -659,24 +659,13 @@ export class AngularCompilerPlugin {
 
       let ngccProcessor: NgccProcessor | undefined;
       if (this._compilerOptions.enableIvy) {
-        let ngcc: typeof import('@angular/compiler-cli/ngcc') | undefined;
-        try {
-          // this is done for the sole reason that @ngtools/webpack
-          // support versions of Angular that don't have NGCC API
-          ngcc = require('@angular/compiler-cli/ngcc');
-        } catch {
-        }
-
-        if (ngcc) {
-          ngccProcessor = new NgccProcessor(
-            ngcc,
-            this._mainFields,
-            compilerWithFileSystems.inputFileSystem,
-            this._warnings,
-            this._errors,
-            this._basePath,
-          );
-        }
+        ngccProcessor = new NgccProcessor(
+          this._mainFields,
+          compilerWithFileSystems.inputFileSystem,
+          this._warnings,
+          this._errors,
+          this._basePath,
+        );
       }
 
       // Create the webpack compiler host.

packages/ngtools/webpack/src/ngcc_processor.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import { Logger } from '@angular/compiler-cli/ngcc';
+import { Logger, process as mainNgcc } from '@angular/compiler-cli/ngcc';
 import { existsSync } from 'fs';
 import * as path from 'path';
 import * as ts from 'typescript';
@@ -29,7 +29,6 @@ export class NgccProcessor {
   private _nodeModulesDirectory: string;
 
   constructor(
-    private readonly ngcc: typeof import('@angular/compiler-cli/ngcc'),
     private readonly propertiesToConsider: string[],
     private readonly inputFileSystem: InputFileSystem,
     private readonly compilationWarnings: (Error | string)[],
@@ -63,7 +62,7 @@ export class NgccProcessor {
 
     const timeLabel = `NgccProcessor.processModule.ngcc.process+${moduleName}`;
     time(timeLabel);
-    this.ngcc.process({
+    mainNgcc({
       basePath: this._nodeModulesDirectory,
       targetEntryPointPath: path.dirname(packageJsonPath),
       propertiesToConsider: this.propertiesToConsider,