mono core dumping on current

[Thomas Klausner <wiz%netbsd.org@localhost>]

On 6.99.3/amd64, I have trouble with a few mono packages that built
fine on 5.99.64.

I've tried rebuilding mono, and this also fails now.
with CFLAGS=-g -O0 I get the following backtrace for the core dump during the 
build:
gmake[5]: Entering directory `/scratch/lang/mono/work/mono-2.10.6/mcs'
/bin/sh .//mkinstalldirs build/deps
mkdir -p -- build/deps
touch build/deps/.stamp
gmake[6]: Entering directory `/scratch/lang/mono/work/mono-2.10.6/mcs'
gmake[6]: gmcs: Command not found
gmake[6]: *** [build/deps/basic-profile-check.exe] Error 127
gmake[6]: Leaving directory `/scratch/lang/mono/work/mono-2.10.6/mcs'
gmake[6]: Entering directory `/scratch/lang/mono/work/mono-2.10.6/mcs'
*** The compiler 'gmcs' doesn't appear to be usable.
*** Trying the 'monolite' directory.
gmake[7]: Entering directory `/scratch/lang/mono/work/mono-2.10.6/mcs'
gmake[8]: Entering directory `/scratch/lang/mono/work/mono-2.10.6/mcs'
[1]   Abort trap (core dumped) MONO_PATH=".//cl...
gmake[8]: *** [build/deps/basic-profile-check.exe] Error 134
gmake[8]: Leaving directory `/scratch/lang/mono/work/mono-2.10.6/mcs'
..
# gdb ../mono/mini/mono mono.core
GNU gdb (GDB) 7.3.1
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64--netbsd".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /scratch/lang/mono/work/mono-2.10.6/mono/mini/mono...done.
[New process 1]
[New process 8]
[New process 7]
[New process 6]
[New process 5]
[New process 4]
[New process 3]
[New process 2]
Core was generated by `mono'.
Program terminated with signal 6, Aborted.
#0  0x00007f7ff70ed9da in _lwp_kill () from /usr/lib/libc.so.12
(gdb) bt
#0  0x00007f7ff70ed9da in _lwp_kill () from /usr/lib/libc.so.12
#1  0x00007f7ff70ed312 in abort () at 
/archive/cvs/src/lib/libc/stdlib/abort.c:74
#2  0x00000000004d7de5 in mono_handle_native_sigsegv (signal=11, 
ctx=0x7f7fffffb3e0) at mini-exceptions.c:2245
#3  0x0000000000420685 in mono_sigsegv_signal_handler (_dummy=11, 
info=0x7f7fffffb360, context=0x7f7fffffb3e0) at mini.c:5848
#4  <signal handler called>
#5  GC_push_all_eager (bottom=0x7f7fffffb7e8 "�\377\377\177\177", 
top=0x7f8008000000 <Address 0x7f8008000000 out of bounds>) at mark.c:1468
#6  0x00000000006b3fa8 in GC_push_all_stack (bottom=0x7f7fffffb7e8 
"�\377\377\177\177", top=0x7f8008000000 <Address 0x7f8008000000 out of bounds>) 
at mark.c:1521
#7  0x00000000006bbecd in pthread_push_all_stacks () at pthread_stop_world.c:297
#8  0x00000000006bbf49 in GC_push_all_stacks () at pthread_stop_world.c:332
#9  0x00000000006b71d2 in GC_default_push_other_roots () at os_dep.c:2255
#10 0x00000000006b53ac in GC_push_roots (all=1, cold_gc_frame=0x7f7fffffb8e4 
"\177\177") at mark_rts.c:646
#11 0x00000000006b1dd7 in GC_mark_some (cold_gc_frame=0x7f7fffffb8e4 
"\177\177") at mark.c:326
#12 0x00000000006abe0a in GC_stopped_mark (stop_func=0x6ab387 
<GC_never_stop_func>) at alloc.c:543
#13 0x00000000006ab9eb in GC_try_to_collect_inner (stop_func=0x6ab387 
<GC_never_stop_func>) at alloc.c:382
#14 0x00000000006b5d6e in GC_init_inner () at misc.c:807
#15 0x00000000006b596b in GC_init () at misc.c:517
#16 0x0000000000574bbc in mono_gc_base_init () at boehm-gc.c:126
#17 0x0000000000598d30 in mono_init_internal (filename=0x7f7fffffe428 
".//class/lib/monolite/mcs.exe", exe_filename=0x7f7fffffe428 
".//class/lib/monolite/mcs.exe", runtime_version=0x0) at domain.c:1286
#18 0x000000000059a0a1 in mono_init_from_assembly (domain_name=0x7f7fffffe428 
".//class/lib/monolite/mcs.exe", filename=0x7f7fffffe428 
".//class/lib/monolite/mcs.exe") at domain.c:1671
#19 0x000000000042140a in mini_init (filename=0x7f7fffffe428 
".//class/lib/monolite/mcs.exe", runtime_version=0x0) at mini.c:6321
#20 0x00000000004ad44b in mono_main (argc=7, argv=0x7f7fffffbdb8) at 
driver.c:1746
#21 0x0000000000412d8e in mono_main_with_options (argc=7, argv=0x7f7fffffbdb8) 
at main.c:66
#22 0x0000000000412dbe in main (argc=7, argv=0x7f7fffffbdb8) at main.c:97

Can someone make something of this?
 Thomas