RFR: 6946: There should be an option to build the agent in the build script

[Miroslav Wengner]

https://bugs.openjdk.java.net/browse/JMC-6946
added: 
- build.sh --packageAgent
- build.sh --runAgentExample

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Commit messages:
 - 6946: cleanup
 - 6946: build script -> build agent, run agent example

Changes: https://git.openjdk.java.net/jmc/pull/183/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=183&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6946
  Stats: 131 lines in 1 file changed: 106 ins; 15 del; 10 mod
  Patch: https://git.openjdk.java.net/jmc/pull/183.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/183/head:pull/183

PR: https://git.openjdk.java.net/jmc/pull/183