RFR: 7904048: Update jtreg to use Ant 1.10.15

[Christian Stein]

On Wed, 25 Jun 2025 12:07:09 GMT, Christian Stein <cstein at openjdk.org> wrote:

> Please review this update to make jtreg use Ant 1.10.15

make/build-support/version-numbers line 30:

> 28: DEFAULT_ANT_VERSION=1.10.8
> 29: DEFAULT_ANT_ARCHIVE_CHECKSUM=dbe187ce2963f9df8a67de8aaff3b0a437d06978
> 30: DEFAULT_ANT_JAR_CHECKSUM=ae148abb0532b685c5eeb22fdec9d124e89be5de

`DEFAULT_ANT_JAR_CHECKSUM` was not used by the build scripts

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PR Review Comment: https://git.openjdk.org/jtreg/pull/270#discussion_r2166573239