Webpak Build Error

```
File "c:\users\rwatts\appdata\local\temp\Bazel.runfiles_s8dqke\runfiles\org_dropbox_rules_node\node\tools\npm\runfiles.py", line 18, in _get_runfiles_dir
raise RunfilesError('Must be run in Bazel environment')
node.tools.npm.runfiles.RunfilesError: Must be run in Bazel environment
Target //:bundle failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 4.455s, Critical Path: 0.84s
INFO: 0 processes.
FAILED: Build did NOT complete successfully
FAILED: Build did NOT complete successfully
```

从 node/tools/npm/runfiles.py 中 _get_runfiles_dir 处报告的 traceback 开始，并使用 --verbose_failures 重新运行 //:bundle 目标，以捕获失败的命令行。当 Bazel 构建在没有 RunfilesError 的情况下成功完成时，即表示完成。

由索引模型根据 Issue 内容生成。