A full source build (dmake without arguments) will not complete.
Building the project vcl (after about 4 hours on my machine (2.6 GHz / 1 Gig
ram) results in a fatal build error. 

Output:

=============
Building project vcl
=============
...
...
Making: ../unxlngi6.pro/lib/libvclplug_gen680li.so
g++ -Wl,-z,combreloc -Wl,-z,defs -Wl,-rpath,'$ORIGIN' -shared
-L../unxlngi6.pro/lib -L../lib -L/usr/local/src/OOB680_m5/solenv/unxlngi6/lib
-L/usr/local/src/OOB680_m5/solver/680/unxlngi6.pro/lib
-L/usr/local/src/OOB680_m5/solenv/unxlngi6/lib -L/usr/local/jdk1.5.0_05/lib
-L/usr/local/jdk1.5.0_05/jre/lib/i386
-L/usr/local/jdk1.5.0_05/jre/lib/i386/client
-L/usr/local/jdk1.5.0_05/jre/lib/i386/native_threads -L/usr/X11R6/lib
../unxlngi6.pro/slo/vclplug_gen_dflt_version.o
../unxlngi6.pro/slo/vclplug_gen_dflt_description.o -o
../unxlngi6.pro/lib/libvclplug_gen680li.so ../unxlngi6.pro/slo/FWS.o
../unxlngi6.pro/slo/salframe.o ../unxlngi6.pro/slo/salobj.o
../unxlngi6.pro/slo/salmenu.o ../unxlngi6.pro/slo/salgdi2.o
../unxlngi6.pro/slo/salbmp.o ../unxlngi6.pro/slo/salgdi.o
../unxlngi6.pro/slo/salvd.o ../unxlngi6.pro/slo/salogl.o
../unxlngi6.pro/slo/dtint.o ../unxlngi6.pro/slo/salcvt.o
../unxlngi6.pro/slo/xfont.o ../unxlngi6.pro/slo/xlfd_attr.o
../unxlngi6.pro/slo/xlfd_extd.o ../unxlngi6.pro/slo/xlfd_smpl.o
../unxlngi6.pro/slo/salgdi3.o ../unxlngi6.pro/slo/pspgraphics.o
../unxlngi6.pro/slo/salprnpsp.o ../unxlngi6.pro/slo/gcach_xpeer.o
../unxlngi6.pro/slo/i18n_cb.o ../unxlngi6.pro/slo/i18n_ic.o
../unxlngi6.pro/slo/i18n_im.o ../unxlngi6.pro/slo/i18n_xkb.o
../unxlngi6.pro/slo/i18n_wrp.o ../unxlngi6.pro/slo/i18n_status.o
../unxlngi6.pro/slo/i18n_keysym.o ../unxlngi6.pro/slo/saldata.o
../unxlngi6.pro/slo/saltimer.o ../unxlngi6.pro/slo/saldisp.o
../unxlngi6.pro/slo/salinst.o ../unxlngi6.pro/slo/salsys.o
../unxlngi6.pro/slo/soicon.o ../unxlngi6.pro/slo/sm.o
../unxlngi6.pro/slo/keysymnames.o ../unxlngi6.pro/slo/wmadaptor.o
../unxlngi6.pro/slo/salsound2.o ../unxlngi6.pro/slo/osssound.o
../unxlngi6.pro/slo/devaudiosound.o ../unxlngi6.pro/slo/audioconvert.o
../unxlngi6.pro/slo/rptpsound.o ../unxlngi6.pro/slo/nassound.o
../unxlngi6.pro/slo/pasfsound.o -lvcl680li -lpsp680li -lsot680li -lutl680li
-ltl680li -lcomphelp4gcc3 -lucbhelper3gcc3 -luno_cppuhelpergcc3 -luno_cppu
-lvos3gcc3 -luno_sal -lsndfile -lportaudio -laudio -lXext -lSM -lICE -lX11 -ldl
-ldl -lpthread -lm -Wl,-Bdynamic -lstlport_gcc
/usr/local/src/OOB680_m5/solver/680/unxlngi6.pro/lib/libaudio.a(ConnSvr.o): In
function `GetAuthorization':
/usr/local/src/OOB680_m5/nas/unxlngi6.pro/misc/build/nas-1.6/lib/audio/ConnSvr.c:1981:
undefined reference to `XauDisposeAuth'
/usr/local/src/OOB680_m5/solver/680/unxlngi6.pro/lib/libaudio.a(ConnSvr.o): In
function `_AuConnectServer':
/usr/local/src/OOB680_m5/nas/unxlngi6.pro/misc/build/nas-1.6/lib/audio/ConnSvr.c:1832:
undefined reference to `XauGetBestAuthByAddr'
collect2: ld gaf exit-status 1 terug
dmake:  Error code 1, while making '../unxlngi6.pro/lib/libvclplug_gen680li.so'
'---* tg_merge.mk *---'

ERROR: Error 65280 occurred while making /usr/local/src/OOB680_m5/vcl/util
dmake:  Error code 1, while making 'build_instsetoo_native'
'---* *---'

Some additional environment info:
Linux version (uname -a): Linux ubuntu 2.6.12-10-386 #1 Fri Apr 28 13:13:44 UTC
2006 i686 GNU/Linux
gcc version: gcc (GCC) 4.0.2 20050808 (prerelease) (Ubuntu 4.0.1-4ubuntu9)
g++ version: g++ (GCC) 4.0.2 20050808 (prerelease) (Ubuntu 4.0.1-4ubuntu9)

I have also tried to full build the code with the gcc-3.3 and gcc-3.4 compilers
with the same result.

I have also done some research and noticed the problem can be reproduced (after
the fatal error has occured) quickly and reproducable by executing the generated
.cmd script in ./vcl/unxlngi6.pro/misc/libvclplug_gen680li.cmd.