RFR: 8374522: Mobile: Add iOS as a platform in OperatingSystem.java

[Kolby Moroz Liebl]

I don't know how but Kotlin calls OperatingSystem.IOS, adding iOS as an OperatingSystem fixed my problems, it had something to do with Kotlin's logging library if I remember correctly during initialization it calls something with OperatingSystem.IOS then it panics because IOS isn't an option in the OperatingSystem Class

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Commit messages:
 - Apply review feedback
 - Add iOS as a platform in OperatingSystem.java

Changes: https://git.openjdk.org/mobile/pull/44/files
  Webrev: https://webrevs.openjdk.org/?repo=mobile&pr=44&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374522
  Stats: 13 lines in 2 files changed: 13 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/mobile/pull/44.diff
  Fetch: git fetch https://git.openjdk.org/mobile.git pull/44/head:pull/44

PR: https://git.openjdk.org/mobile/pull/44