fix(nextjs): Fix SDK multiplexer loader on Windows (#6866)

Author: lforst

packages/nextjs/src/config/webpack.ts

@@ -70,10 +70,10 @@ export function constructWebpackConfigFunction(
     addValueInjectionLoader(newConfig, userNextConfig, userSentryOptions);
 
     newConfig.module.rules.push({
-      test: /node_modules\/@sentry\/nextjs/,
+      test: /node_modules[/\\]@sentry[/\\]nextjs/,
       use: [
         {
-          loader: path.resolve(__dirname, 'loaders/sdkMultiplexerLoader.js'),
+          loader: path.resolve(__dirname, 'loaders', 'sdkMultiplexerLoader.js'),
           options: {
             importTarget: buildContext.nextRuntime === 'edge' ? './edge' : './client',
           },
@@ -133,7 +133,7 @@ export function constructWebpackConfigFunction(
           },
           use: [
             {
-              loader: path.resolve(__dirname, 'loaders/wrappingLoader.js'),
+              loader: path.resolve(__dirname, 'loaders', 'wrappingLoader.js'),
               options: {
                 pagesDir: pagesDirPath,
                 pageExtensionRegex,