[jdk17u-dev] RFR: 8311645: Memory leak in jspawnhelper spawnChild after JDK-8307990

[Volker Simonis]

This is a clean backport of [JDK-8311645: Memory leak in jspawnhelper spawnChild after JDK-8307990](https://bugs.openjdk.org/browse/JDK-8311645) which is a follow-up fix for [JDK-8307990: jspawnhelper must close its writing side of a pipe before reading from it](https://bugs.openjdk.org/browse/JDK-8307990) which is currently [under review](https://github.com/openjdk/jdk17u-dev/pull/2013).

This backport depends on [pr/2013](https://github.com/openjdk/jdk17u-dev/pull/2013) and will be pushed once that one has been reviewed and approved.

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Depends on: https://git.openjdk.org/jdk17u-dev/pull/2013

Commit messages:
 - Backport 401c3dea5d8823bc9c0f40506ddad46e983ebf68

Changes: https://git.openjdk.org/jdk17u-dev/pull/2017/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2017&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311645
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2017.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2017/head:pull/2017

PR: https://git.openjdk.org/jdk17u-dev/pull/2017