hg: build-infra/jdk9: Improve behavior of new feature-based build.

[magnus.ihse.bursie at oracle.com]

Changeset: 5d30fcf28853
Author:    ihse
Date:      2015-10-09 17:03 +0200
URL:       http://hg.openjdk.java.net/build-infra/jdk9/rev/5d30fcf28853

Improve behavior of new feature-based build.

! common/autoconf/generated-configure.sh
! common/autoconf/jdk-options.m4
! common/autoconf/spec.gmk.in
! make/common/MakeBase.gmk