feat(@ngtools/webpack): add path mappings resolution to NGCC

In version 8.1, similar to TypeScript Compiler, NGCC supports Path Mappings. This enable NGCC to process workspace libraries similar to what it is currently being done for `node_modules`

Closes angular#14594

Author: alan-agius4

src/angular_compiler_plugin.ts

@@ -667,6 +667,7 @@ export class AngularCompilerPlugin {
           this._warnings,
           this._errors,
           this._basePath,
+          this._compilerOptions,
         );
       }
 

src/ngcc_processor.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import { Logger, process as mainNgcc } from '@angular/compiler-cli/ngcc';
+import { Logger, PathMappings, process as mainNgcc } from '@angular/compiler-cli/ngcc';
 import { existsSync } from 'fs';
 import * as path from 'path';
 import * as ts from 'typescript';
@@ -27,16 +27,26 @@ export class NgccProcessor {
   private _processedModules = new Set<string>();
   private _logger: NgccLogger;
   private _nodeModulesDirectory: string;
+  private _pathMappings: PathMappings | undefined;
 
   constructor(
     private readonly propertiesToConsider: string[],
     private readonly inputFileSystem: InputFileSystem,
     private readonly compilationWarnings: (Error | string)[],
     private readonly compilationErrors: (Error | string)[],
     private readonly basePath: string,
+    private readonly compilerOptions: ts.CompilerOptions,
   ) {
     this._logger = new NgccLogger(this.compilationWarnings, this.compilationErrors);
     this._nodeModulesDirectory = this.findNodeModulesDirectory(this.basePath);
+
+    const { baseUrl, paths } = this.compilerOptions;
+    if (baseUrl && paths) {
+      this._pathMappings = {
+        baseUrl,
+        paths,
+      };
+    }
   }
 
   processModule(
@@ -69,6 +79,7 @@ export class NgccProcessor {
       compileAllFormats: false,
       createNewEntryPointFormats: true,
       logger: this._logger,
+      pathMappings: this._pathMappings,
     });
     timeEnd(timeLabel);