engine: fix logging example not writing to file

The log file `jit.log` created in the bal_logging.h example was empty.

Signed-off-by: Ronald Caesar <github43132@proton.me>

include/bal_logging.h

@@ -49,6 +49,7 @@
 //! };
 //!
 //! BAL_LOG_DEBUG(&logger, "Writing to custom file backend");
+//! fclose(log_file);
 //! ```
 
 #ifndef BALLISTIC_LOGGING_H

tools/doctest.py

@@ -7,7 +7,7 @@ import tempfile
 from typing import List, Optional
 
 CC: str  = "clang"
-CFLAGS: List[str] = ["-Wall", "-Werror"]
+CFLAGS: List[str] = ["-Wall", "-Werror", "-DBAL_MAX_LOG_LEVEL=4"]
 
 if os.name == "nt":
     CFLAGS.append("-D_CRT_SECURE_NO_WARNINGS")