hg: build-infra/jdk9: Allow EXTRA_FLAGS to be changed by custom extensions, export HOTSPOT_DEBUG_LEVEL to spec.gmk

[ingemar.aberg at oracle.com]

Changeset: d7c4a1755e06
Author:    iaberg
Date:      2015-11-17 11:32 +0100
URL:       http://hg.openjdk.java.net/build-infra/jdk9/rev/d7c4a1755e06

Allow EXTRA_FLAGS to be changed by custom extensions, export HOTSPOT_DEBUG_LEVEL to spec.gmk

! common/autoconf/generated-configure.sh
! common/autoconf/hotspot.m4
! common/autoconf/spec.gmk.in