RFR: 8315383: jlink SystemModulesPlugin incorrectly parses the options

[Oliver Kopp]

Fixes https://bugs.openjdk.org/browse/JDK-8315383

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Commit messages:
 - 8315383: jlink SystemModulesPlugin incorrectly parses the options

Changes: https://git.openjdk.org/jdk/pull/15495/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15495&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315383
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15495.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15495/head:pull/15495

PR: https://git.openjdk.org/jdk/pull/15495