git: openjdk/jdk20u: master: 8302879: doc/building.md update link to jtreg builds

[George Adams]

Changeset: c6a25f47
Author:    George Adams <gdams at openjdk.org>
Date:      2023-02-21 13:14:17 +0000
URL:       https://git.openjdk.org/jdk20u/commit/c6a25f47fbf02614d622ef550bccbf5482109061

8302879: doc/building.md update link to jtreg builds

Backport-of: bb3dfd6adbb58871bc7238107ed254831b22d48b

! doc/building.html
! doc/building.md