A quick make revealed a problem:
>>>Recursively making sound all @ Wed Sep 19 23:00:57 ADT 2007 ...
make: Entering directory `/home/damoursda/workspace-openjdk/openjdk/j2se/make/javax/sound'
Makefile:64: ../../common/BinaryPlugs.gmk: No such file or directory
make: *** No rule to make target `../../common/BinaryPlugs.gmk'. Stop.
Performing a make clean and trying again didn’t help.
It turns out that there is a bug in build 20 of OpenJDK. It turns out that two Makefiles have the wrong path for BinaryPlugs.gmk. It is necessary to change the paths from $(BUILDDIR)/common/BinaryPlugs.gmk to $(BUILDDIR)/common/internal/BinaryPlugs.gmk in both j2se/make/javax/sound/Makefile and in j2se/make/javax/sound/jsoundhs/Makefile.
Running a make after making these changes gives me a shiny new compiled JDK.
I am quite surprised that a problem this large would be released in a milestone build. I would have though that any continuous build or even simple smokescreen testing would have picked up this problem.