index_build.py: Set exist_ok when creating fuzzing engine dir

To enable rebuilding indexes.

PiperOrigin-RevId: 776041859

Author: OSS-Fuzz Team

infra/base-images/base-builder/indexer/index_build.py

@@ -248,7 +248,7 @@ def copy_fuzzing_engine() -> Path:
   fuzzing_engine_dir = SRC / PROJECT
   if not fuzzing_engine_dir.exists():
     fuzzing_engine_dir = SRC / 'fuzzing_engine'
-    fuzzing_engine_dir.mkdir()
+    fuzzing_engine_dir.mkdir(exist_ok=True)
 
   shutil.copy('/opt/indexer/fuzzing_engine.cc', fuzzing_engine_dir)
   return fuzzing_engine_dir