RFR: Add SKARA_JAVA_OPTS env variable to launchers

[Erik Joelsson]

This change adds the possibility of adding java options used when running a Skara image (such as the bots) though the environment variable SKARA_JAVA_OPTS.

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Commit messages:
 - Add SKARA_JAVA_OPTS env variable to launchers

Changes: https://git.openjdk.java.net/skara/pull/1158/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1158&range=00
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/1158.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1158/head:pull/1158

PR: https://git.openjdk.java.net/skara/pull/1158