message: Ensure customConfig is deep cloned to avoid side affects
diff: @@ -185,7 +185,7 @@ function runCdkVersionMatch(packageJson, cliInfo) {
  async function loadEsbuildConfigOverrides(customConfig) {
  // Handle deprecated string format
  - customConfig = customConfig || {};
  + customConfig = JSON.parse(JSON.stringify(customConfig || {}));
  // note: "esbuildConfig" used to take a string, a path to the user
  // provided config file. With the new format, esbuildConfig is
  // configured inline, and the external file can only be used
  