RFR: 8274548: (fc) FileChannel gathering write fails with IOException "Invalid argument" on macOS 11.6

[Brian Burkhalter]

On macOS, handle the case where `writev()` is given an array of `struct iovec` the sum of whose `iov_len` fields overflows `INT_MAX`.

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Commit messages:
 - 8274548: (fc) FileChannel gathering write fails with IOException "Invalid argument" on macOS 11.6

Changes: https://git.openjdk.java.net/jdk/pull/5831/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5831&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274548
  Stats: 161 lines in 2 files changed: 160 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5831.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5831/head:pull/5831

PR: https://git.openjdk.java.net/jdk/pull/5831