PR #12633: Fix handling of unknown flags in the multihost HLO runner.
PR #12633: Fix handling of unknown flags in the multihost HLO runner.

Imported from GitHub PR https://github.com/openxla/xla/pull/12633

Fixes https://github.com/openxla/xla/issues/7923
Copybara import of the project:

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71083c7d6dfdcaec1a5458b3f1cd04b11e13f8bd by Ilia Sergachev <isergachev@nvidia.com>:

Fix handling of unknown flags in the multihost HLO runner.

Merging this change closes #12633

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/12633 from openxla:fix_multihost_runner_flag_parsing 71083c7d6dfdcaec1a5458b3f1cd04b11e13f8bd
