RFR: 6910: Missing manifest prevents agent jar from running

[Gunnar Morling]

6910: Missing manifest prevents agent jar from running

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Commit messages:
 - 6910: Adding MANIFEST.MF to agent JAR

Changes: https://git.openjdk.java.net/jmc/pull/122/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=122&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6910
  Stats: 24 lines in 1 file changed: 12 ins; 12 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/122.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/122/head:pull/122

PR: https://git.openjdk.java.net/jmc/pull/122