I ran into the xen sched_ctl.h issue, and nuked my objdir, and restarted
build.sh.  After nbmake was built, I got a segfault.  Digging in, I
found that it was running nbmake after it was linked that was the
problem.  I modified buidlmake.sh to set HOST_CFLAGS to -g instead of
-O.  After building, I ran it:

(gdb) run
Starting program: /tmp/nbbuild8631/nbmake 

Program received signal SIGSEGV, Segmentation fault.
0x0806715b in Var_Parse (str=0x8068df4 "${.MAKE.JOB.PREFIX}", ctxt=0x8070000, 
    errnum=0, lengthPtr=0xbfbfdf58, freePtr=0xbfbfdf54)
    at /n0/gdt/NetBSD-current/src/tools/make/../../usr.bin/make/var.c:3330
3330            *WR(tstr) = '\0';
(gdb) print tstr
$1 = 0x8068e06 "}"


This is with up-to-date -current, and the host is within a few months
netbsd-4.  I am trying to build for i386 on i386.

This feels like writing shared strings, but I really don't know what's
wrong.