Fix that bitproto may break on bitproto -q -c options

Author: hit9

compiler/bitproto/_main.py

@@ -137,6 +137,7 @@ def main(
         fatal(str(error))
 
     # Lint
+    lint_warnings = 0
     if not disable_linter:
         lint_warnings = lint(proto)
 

compiler/bitproto/utils.py

@@ -8,6 +8,7 @@
     Any,
     Callable,
     List,
+    NoReturn,
     Optional,
     Type as T,
     TypeVar,
@@ -292,7 +293,7 @@ def write_stderr(s: str) -> None:
     sys.stderr.write(s + "\n")
 
 
-def fatal(s: str = "", code: int = 1) -> None:
+def fatal(s: str = "", code: int = 1) -> NoReturn:
     """Exit the whole program with given code and message."""
     if s:
         write_stderr(s)