hg: jdk9/sandbox: Adding text.

[magnus.ihse.bursie at oracle.com]

Changeset: 36a0a2e2dc42
Author:    ihse
Date:      2017-06-16 20:53 +0200
URL:       http://hg.openjdk.java.net/jdk9/sandbox/rev/36a0a2e2dc42

Adding text.

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