hg: build-infra/jdk9: Add make/test/BuildTestLib.gmk as a proper way of building test-lib.jar and wb.jar.

[magnus.ihse.bursie at oracle.com]

Changeset: d19eb9753d24
Author:    ihse
Date:      2015-08-24 10:53 +0200
URL:       http://hg.openjdk.java.net/build-infra/jdk9/rev/d19eb9753d24

Add make/test/BuildTestLib.gmk as a proper way of building test-lib.jar and wb.jar.

! make/Main.gmk
+ make/test/BuildTestLib.gmk