FixTextMemMapDataset index file creation in multi-node setup

[gheinrich]

What does this PR do ?

Fixes issue #6715 by creating index files on all processes with local_rank 0.

Collection: NLP

Changelog

• Update rank condition to create index files when local_rank is 0 (formerly when global_rank was 0).

Usage

• No change in used.

Before your PR is "Ready for review"

Pre checks:

• Make sure you read and followed Contributor guidelines
• Did you write any new necessary tests?
• Did you add or update any necessary documentation?
• Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  • Reviewer: Does the PR have correct import guards for all optional libraries?

PR Type:

• New Feature
• Bugfix
• Documentation

Who can review?

Anyone in the community is free to review the PR once the checks have passed.
Contributor guidelines contains specific people who can review PRs to various areas.

Additional Information

• Related to TextMemMapDataset assumes shared storage between nodes #6715

[gheinrich]

Hi @michalivne , would you mind taking a look? Thank you!

[michalivne]

LGTM! Minor question.