Ensure loaderFile is included in webpack cache key (#43315)

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## Bug

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- [ ] Integration tests added
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packages/next/build/webpack-config.ts

@@ -2298,6 +2298,7 @@ export default async function getBaseWebpackConfig(
     emotion: config.compiler?.emotion,
     modularizeImports: config.experimental?.modularizeImports,
     legacyBrowsers: config.experimental?.legacyBrowsers,
+    imageLoaderFile: config.images.loaderFile,
   })
 
   const cache: any = {