fix(js): not generate tsconfig if already exists (#29317)

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## Current Behavior
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- in serve target, it uses executor `@nx/webpack:dev-server`
- in `packages/webpack/src/executors/dev-server/dev-server.impl.ts`,
when buildLibsFromSource is false, it calls createTmpTsConfig to create
a temp config
- in webpack.config.js, it has `module.exports =
composePlugins(withNx()`. in withNx, it calls
NxTsconfigPathsWebpackPlugin.
- when buildLibsFromSource is false, it called createTmpTsConfig again
based on the temp config. it created an infinite loop because it creates
a tsconfig that extends itself.

## Expected Behavior
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- do not create a temp config if it is a generated ts config

## Related Issue(s)
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merged. -->

Fixes https://github.com/nrwl/nx/issues/28006

packages/js/src/utils/buildable-libs-utils.ts

@@ -445,6 +445,9 @@ export function createTmpTsConfig(
     process.env.NX_TASK_TARGET_TARGET ?? 'build',
     'tsconfig.generated.json'
   );
+  if (tsconfigPath === tmpTsConfigPath) {
+    return tsconfigPath;
+  }
   const parsedTSConfig = readTsConfigWithRemappedPaths(
     tsconfigPath,
     tmpTsConfigPath,