add aarch64/shenandoah support for jdk8

[judovana]

This issue was pinpointed as regression in #848

Fedora and rhel are shipping jdk8 from downstream forest which originally included aarch64 and shenandoah for jdk8 projects. Later the aarch64 proejct got merged to upstream, and only shenandoah feature remained here.

Temurin jdk shouold consider to build also from aarch64-shenandoah repository ionstead of vanilla upstream.

Slightly more info in #848

@jiekang fyi!