support whatever.BUILD bazel files

It's common for external bazel workspaces to use external-project.BUILD files, as opposed to BUILD.bazel files. This is to differentiate them from the local workspace's bazel files. Hence, it would be good to treat these files like bazel files as well.

identify/extensions.py

@@ -206,6 +206,7 @@
     '.yamllint': EXTENSIONS['yaml'] | {'yamllint'},
     '.zshrc': EXTENSIONS['zsh'],
     'AUTHORS': EXTENSIONS['txt'],
+    '.BUILD': {'text', 'bazel'},
     'BUILD.bazel': {'text', 'bazel'},
     'BUILD': {'text', 'bazel'},
     'CMakeLists.txt': EXTENSIONS['cmake'],