fix(@angular-devkit/build-optimizer): support windows paths in rollup plugin

Author: filipesilva

packages/angular_devkit/build_optimizer/src/build-optimizer/rollup-plugin.ts

@@ -23,11 +23,17 @@ export interface Options {
 }
 
 export default function optimizer(options: Options) {
+  // Normalize paths for comparison.
+  if (options.sideEffectFreeModules) {
+    options.sideEffectFreeModules = options.sideEffectFreeModules.map(p => p.replace(/\\/g, '/'));
+  }
+
   return {
     name: 'build-optimizer',
     transform: (content: string, id: string): {code: string, map: RawSourceMap}|null => {
+      const normalizedId = id.replace(/\\/g, '/');
       const isSideEffectFree = options.sideEffectFreeModules &&
-        options.sideEffectFreeModules.some(m => id.indexOf(m) >= 0);
+        options.sideEffectFreeModules.some(m => normalizedId.indexOf(m) >= 0);
       const { content: code, sourceMap: map } = buildOptimizer({
         content, inputFilePath: id, emitSourceMap: true, isSideEffectFree,
       });