RFR: 7904048: Update jtreg to use Ant 1.10.15 [v2]

[Christian Stein]

> Please review this update to make jtreg use Ant 1.10.15

Christian Stein has updated the pull request incrementally with one additional commit since the last revision:

  Set `ANT_HOME` environment variable

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Changes:
  - all: https://git.openjdk.org/jtreg/pull/270/files
  - new: https://git.openjdk.org/jtreg/pull/270/files/2a8e5570..07168bd3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=270&range=01
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=270&range=00-01

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jtreg/pull/270.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/270/head:pull/270

PR: https://git.openjdk.org/jtreg/pull/270