ICU-22714 fix zos build with openXL

[alexgubanow]

Checklist

• [x] Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22714
• [x] Required: The PR title must be prefixed with a JIRA Issue number.
• [x] Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• [ ] Required: Each commit message must be prefixed with a JIRA Issue number. - this is a draft branch, to get attention and help
• [ ] Issue accepted (done by Technical Committee after discussion)
• [ ] Tests included, if applicable
• [ ] API docs and/or User Guide docs changed or added, if applicable

[CLAassistant]

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1 out of 2 committers have signed the CLA.

:white_check_mark: alexgubanow
:x: ohubanov

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[alexgubanow]

will cancel this PR and open a new one with one commit, following all rules