thrift bazel modules conflicts on macos m1

Hello Babylon maintainers, our project uses BRPC and we encountered the following issue when compiling on the macOS M1 platform.

```
ERROR: /private/var/tmp/_bazel_distiller/bedaa68a8664d1b29e96b826d058247f/external/bazel_tools/tools/build_defs/repo/utils.bzl:120:15: An error occurred during the fetch of repository 'thrift~':
Traceback (most recent call last):
File "/private/var/tmp/_bazel_distiller/bedaa68a8664d1b29e96b826d058247f/external/bazel_tools/tools/build_defs/repo/http.bzl", line 148, column 26, in _http_archive_impl
download_remote_files(ctx)
File "/private/var/tmp/_bazel_distiller/bedaa68a8664d1b29e96b826d058247f/external/bazel_tools/tools/build_defs/repo/utils.bzl", line 120, column 15, in download_remote_files
p.wait()
Error in wait: java.io.IOException: Error downloading [https://baidu.github.io/babylon/registry/modules/thrift/0.21.0/overlay/BUILD] to /private/var/tmp/_bazel_distiller/bedaa68a8664d1b29e96b826d058247f/external/thrift~/BUILD: /private/var/tmp/_bazel_distiller/bedaa68a8664d1b29e96b826d058247f/external/thrift~/BUILD (Is a directory)
```

The reason might be that the macOS file system is case-insensitive, and thrift has a 'build' directory that conflicts with the Bazel 'BUILD' file.

Start by reproducing the fetch on macOS M1 and inspect the thrift overlay at registry/modules/thrift/0.21.0/overlay/BUILD, along with the reported external/thrift~ path. Confirm the case-insensitive directory collision and verify that the thrift module fetch completes without treating BUILD as a directory.

Written by the indexing model from the issue text.