community/apache-ant: let builder resolve java-jdk & use default-jvm
this allows for building with openjdk21 (or later) where available, enabling this aport also on riscv64, and still builds with openjdk8 on 32bit architectures
This reverts commit b298af55.
only openjdk21 is available for riscv64, but at the same time it is not available for 32bit architectures, perhaps the builders are now able to resolve the provivides and depends="java-jdk" is enough