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
```

Start with the reported traceback in node/tools/npm/runfiles.py at _get_runfiles_dir and rerun the //:bundle target with --verbose_failures to capture the failed command lines. Done means the Bazel build completes successfully without the RunfilesError.

Written by the indexing model from the issue text.