Okay, this time it failed with:

gcc -O2 -DSGI -DUSE_TRACING -DHAVE_XDBE -UUSE_TRACING -DDONT_USE_MCW_MAL
LOC -o to3d to3d.o -s -L. -L/usr/Motif-2.1 -lmrix -lcoxplot -lmri -lf2c -lmri -l
Xm -lXt -lXext -lX11 -lm
ld32: WARNING 84: ./libmri.a is not used for resolving any symbol.
ld32: Segmentation fault. Removing output file...
collect2: ld returned 1 exit status

and when you try to run afni (which is in the src folder still, not in the INSTALLDIR location from the Makefile), it pops up the splashscreen briefly, then the shell displays the following:

..
** Version check: [afni.nimh.nih.gov]

GPL AFNI: Analysis of Functional NeuroImages, by RW Cox (rwcox@nih.gov)
This is Version 2.55d of 08 Aug 2003

** This software was designed to be used only for research purposes. **
** Clinical uses are not recommended, and have never been evaluated. **
** This software comes with no warranties of any kind whatsoever, **
** and may not be useful for anything. Use it at your own risk! **
** If these terms are not acceptable, you aren't allowed to use AFNI.**
** See 'Define Datamode->Misc->License Info' for more details. **

Thanks go to SM Rao for useful feedback

Initializing: X11.. Widgets...... Input files:
*** No datasets or sessions input -- Dummy dataset created.*** EDIT_dset_items: illegal new nxyz
*** EDIT_dset_items: illegal opcode = 2147428640 at arg #6
*** EDIT_dset_items: illegal opcode = -1024458752 at arg #8

3 errors creating dummy dataset!
12% ** Version Check: fails to complete **

--Nick