[clang-tidy] For `run-clang-tidy.py` do not treat `allow_enabling_alpha_checkers` as a none value.

[Abpostelnicu]

Summary

allow_enabling_alpha_checkers will never be None, it will be True or False from argparse so threat it accordingly.
The issue has been discovered by felixn

[JonasToth]

LGTM

[xgupta]

This was committed in https://github.com/llvm/llvm-project/commit/03ded5497a2f458b6af054fa7bac0da0240e7b7a.

clang-tools-extra/clang-tidy/tool/run-clang-tidy.py

def make_absolute(f, directory):
   return os.path.normpath(os.path.join(directory, f))
 
 
 def get_tidy_invocation(f, clang_tidy_binary, checks, tmpdir, build_path,
                         header_filter, allow_enabling_alpha_checkers,
                         extra_arg, extra_arg_before, quiet, config):
   """Gets a command line for clang-tidy."""
   start = [clang_tidy_binary]
-  if allow_enabling_alpha_checkers is not None:
+  if allow_enabling_alpha_checkers:
     start.append('-allow-enabling-analyzer-alpha-checkers')
   if header_filter is not None:
     start.append('-header-filter=' + header_filter)
   if checks:
     start.append('-checks=' + checks)
   if tmpdir is not None:
     start.append('-export-fixes')
     # Get a temporary file. We immediately close the handle so clang-tidy can