hg: jdk/sandbox: Add documentation. Prefer --enable-FEAT to --with-..=FEAT.

[magnus.ihse.bursie at oracle.com]

Changeset: f44f4707b690
Author:    ihse
Date:      2020-02-19 10:33 +0100
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/f44f4707b690

Add documentation. Prefer --enable-FEAT to --with-..=FEAT.

! doc/building.html
! doc/building.md
! make/autoconf/jvm-features.m4
! make/conf/jib-profiles.js
! src/hotspot/.mx.jvmci/mx_jvmci.py