How to compile an OpenJDK 7 debug build on Ubuntu

Where can I find a simple set of instructions to compile an OpenJDK 7 debug build on Ubuntu 11.10 (Oneiric)? A debug build would make more JVM options available for troubleshooting purposes; for example, WizardMode. The developers' guide and build README have a lot of noise and are hard to follow.

Install relevant packages:

sudo apt-get install ant build-essential openjdk-6-jdk
sudo apt-get build-dep openjdk-6-jdk

Find the master OpenJDK Mercurial repository you want to start from. These instructions will use jdk7u2.
Command examples contain settings to allow Internet access through a proxy server; remove them if they are unnecessary for you.
Clone the Mercurial top-level forest repository:

$ mkdir jdk7u2
$ cd jdk7u2
$ hg --config http_proxy.host=proxy:1234 clone http://hg.openjdk.java.net/jdk7u/jdk7u2 forest
$ cd forest
$ sh ./get_source.sh

The build will fail while compiling the sound libraries. As suggested here, use the following to patch the appropriate Makefile:

$ echo -e "--- old/jdk/make/javax/sound/jsoundalsa/Makefile    2012-01-28 12:00:00.000000000 -0500\n+++ new/jdk/make/javax/sound/jsoundalsa/Makefile    2012-01-28 12:00:00.000000000 -0500\n@@ -65,7 +65,7 @@\n \t\$(MIDIFILES_export) \\\\\n \t\$(PORTFILES_export)\n\n-LDFLAGS += -lasound\n+EXTRA_LIBS += -lasound\n \n CPPFLAGS += \\\\\n \t-DUSE_DAUDIO=TRUE \\\\" | patch -p1

Compile:

$ export LANG=C ALT_BOOTDIR=/usr/lib/jvm/java-6-openjdk ANT_OPTS="-Dhttp.proxyHost=proxy -Dhttp.proxyPort=1234 -Dhttps.proxyHost=proxy -Dhttps.proxyPort=1234"
$ . jdk/make/jdk_generic_profile.sh
$ make ALLOW_DOWNLOADS=true fastdebug_build

The compile will take a while.
Verify the build:

$ build/linux-amd64-fastdebug/j2sdk-image/bin/java -version
openjdk version "1.7.0-internal-fastdebug"
OpenJDK Runtime Environment (build 1.7.0-internal-fastdebug-user_2012_01_28_13_25-b00)
OpenJDK 64-Bit Server VM (build 22.0-b10-fastdebug, mixed mode)
$ build/linux-amd64-fastdebug/j2sdk-image/bin/java -XX:+AggressiveOpts -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal -XX:+PrintFlagsWithComments -version