RFR: CODETOOLS-7903104: Remove secondary Ant build system

[Jonathan Gibbons]

Please review a change to remove support for the old secondary Ant-based build system.

It is no longer used or supported.

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Commit messages:
 - Merge with upstream/master
 - CODETOOLS-7903104: Remove secondary Ant build system

Changes: https://git.openjdk.java.net/jtreg/pull/59/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtreg&pr=59&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903104
  Stats: 634 lines in 4 files changed: 0 ins; 634 del; 0 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/59.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/59/head:pull/59

PR: https://git.openjdk.java.net/jtreg/pull/59