RFR: 7903044: Report `os.*` system properties in .jtr file

[Christian Stein]

https://bugs.openjdk.java.net/browse/CODETOOLS-7903044

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Commit messages:
 - Report `os.*` system properties in .jtr file

Changes: https://git.openjdk.java.net/jtreg/pull/35/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtreg&pr=35&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903044
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/35.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/35/head:pull/35

PR: https://git.openjdk.java.net/jtreg/pull/35