fix(@schematics/angular): polyfills migration leaving broken code in windows

Replacment of line endings should only happen to increase the hash matches as otherwise the recorder will fail to update the correct positions

Fixes angular#14443

Author: Alan Agius

packages/schematics/angular/migrations/update-8/drop-es6-polyfills.ts

@@ -78,12 +78,11 @@ function dropES2015PolyfillsFromFile(polyfillPath: string): Rule {
       return;
     }
 
-    // normalize line endings to increase hash match chances
-    const content = source.toString().replace(/\r\n|\r/g, '\n');
-
+    const content = source.toString();
     // Check if file is unmodified, if so then replace and return
     const hash = createHash('md5');
-    hash.update(content);
+    // normalize line endings to increase hash match chances
+    hash.update(content.replace(/\r\n|\r/g, '\n'));
     const digest = hash.digest('hex');
     if (knownPolyfillHashes.includes(digest)) {
       // Replace with new project polyfills file