RFR: 6889: Provide build script for making it easier to build JMC

[Schalli1987]

Second try, I signed the OCA last week (also I do not have any response).

This script provides an easy way to package JMC by just calling a single command.

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Commit messages:
 - Merge remote-tracking branch 'origin/master' into enhancement/buildScript
 - fix path to jmc in output
 - Merge remote-tracking branch 'origin/master' into enhancement/buildScript
 - Add build script for linux

Changes: https://git.openjdk.java.net/jmc/pull/100/files
 Webrev: https://webrevs.openjdk.java.net/jmc/100/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6889
  Stats: 170 lines in 2 files changed: 170 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/100.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/100/head:pull/100

PR: https://git.openjdk.java.net/jmc/pull/100