Check properly whether SWC is used or not when using forceSwcTransfor…

…ms (#42531)

Check whether SWC is used or not by checking "useSWCLoader" variable, not by checking "babelConfigFile".
Since we can bypass babel config file by turning on experimental.forceSwcTransforms, we should not check babel by its config file.



Co-authored-by: JJ Kasper <22380829+ijjk@users.noreply.github.com>

packages/next/build/webpack-config.ts

@@ -660,7 +660,7 @@ export default async function getBaseWebpackConfig(
     loggedIgnoredCompilerOptions = true
   }
 
-  if (babelConfigFile && config.experimental.fontLoaders) {
+  if (!useSWCLoader && babelConfigFile && config.experimental.fontLoaders) {
     Log.error(
       `"experimental.fontLoaders" is enabled which requires SWC although Babel is being used due to custom babel config being present "${path.relative(
         dir,