[TypeSpec CI] Fail if folder does not exist (Azure#24451)

- Fixes Azure#24448

Author: mikeharder

eng/pipelines/templates/steps/typespec-ci.yml

@@ -13,7 +13,7 @@ steps:
     # Log commands before running
     set -x
 
-    pushd ${{parameters.Folder}}
+    pushd ${{parameters.Folder}} || exit_code=1
 
     actual_npm_prefix=$(npm prefix)