[lworld] RFR: 8367592: Call to write_flat_field uses a Windows calling convention arg

[David Simms]

Work-around with r11

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Commit messages:
 - 8367592: Call to write_flat_field uses a Windows calling convention arg

Changes: https://git.openjdk.org/valhalla/pull/1585/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1585&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367592
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/valhalla/pull/1585.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1585/head:pull/1585

PR: https://git.openjdk.org/valhalla/pull/1585