git: openjdk/jdk11u-dev: 8251549: Update docs on building for Git

[Severin Gehwolf]

Changeset: ba097cae
Author:    Severin Gehwolf <sgehwolf at openjdk.org>
Date:      2021-08-23 08:19:29 +0000
URL:       https://git.openjdk.java.net/jdk11u-dev/commit/ba097caea1d491054e2a89ce5a3c0b06173ac96d

8251549: Update docs on building for Git

Reviewed-by: shade, clanger
Backport-of: 042734cc5b17302a8f2ecdf577511bd6d5ec5e22

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