fix(@angular-devkit/build-angular): skip downlevel processing of assets (#15433)

* fix(@angular-devkit/build-angular): identify asset emitted files

* fix(@angular-devkit/build-angular): skip downlevel processing of assets

Fixes #15423

Author: clydin

packages/angular_devkit/build_angular/src/browser/index.ts

@@ -289,6 +289,11 @@ export function buildWebpackBrowser(
               const actions: ProcessBundleOptions[] = [];
               const seen = new Set<string>();
               for (const file of emittedFiles) {
+                // Assets are not processed nor injected into the index
+                if (file.asset) {
+                  continue;
+                }
+
                 // Scripts and non-javascript files are not processed
                 if (
                   file.extension !== '.js' ||

packages/angular_devkit/build_webpack/src/utils.ts

@@ -13,6 +13,7 @@ export interface EmittedFiles {
   name?: string;
   file: string;
   initial: boolean;
+  asset?: boolean;
   extension: string;
 }
 
@@ -42,7 +43,7 @@ export function getEmittedFiles(compilation: webpack.compilation.Compilation): E
 
   // other all files
   for (const file of Object.keys(compilation.assets)) {
-    files.push({ file, extension: path.extname(file), initial: false });
+    files.push({ file, extension: path.extname(file), initial: false, asset: true });
   }
 
   // dedupe