RFR: 8308943: jdk.internal.le build fails on AIX

[Jan Lahoda]

A simpler alternative to https://github.com/openjdk/jdk/pull/14176 - it only creates a stub of `JDKNativePty` for AIX, throwing `UnsupportedOperationException`. JLine will then either use the next provider (i.e. "exec", for JShell), or dumb terminal.

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Commit messages:
 - 8308943: jdk.internal.le build fails on AIX

Changes: https://git.openjdk.org/jdk/pull/14247/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14247&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308943
  Stats: 51 lines in 1 file changed: 51 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14247.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14247/head:pull/14247

PR: https://git.openjdk.org/jdk/pull/14247