RFR: 8274548: (fc) FileChannel gathering write fails with IOException "Invalid argument" on macOS 11.6 [v6]

[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`.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8274548: Minor restructuring of get_darwin_version() and writevMax()

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5831/files
  - new: https://git.openjdk.java.net/jdk/pull/5831/files/f03fc290..e44a468c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5831&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5831&range=04-05

  Stats: 18 lines in 1 file changed: 8 ins; 0 del; 10 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