[jdk8u-dev] RFR: 8239365: ProcessBuilder test modifications for AIX execution

[Ilarion Nakonechnyy]

Applied cleanly, fixes JTREG failed test java/lang/ProcessBuilder/Basic.java on AIX 7.2

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Commit messages:
 - Backport 2785fe5621bd3af64450f1f5069dc2a4b47785fe

Changes: https://git.openjdk.org/jdk8u-dev/pull/348/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=348&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8239365
  Stats: 11 lines in 1 file changed: 4 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/348.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/348/head:pull/348

PR: https://git.openjdk.org/jdk8u-dev/pull/348