[plt-scheme] Segfault on OpenBSD

Hi,

mzscheme 301.12 builds without issue on OpenBSD 3.8 (once I edit  
libffi configure script). However, it segfaults immediately on  
startup. Running it in GDB shows that GC_find_limit() in os_dep.c  
seems to be the problem:

Starting program: /home/patrick/plt/src/mzscheme/mzscheme

Program received signal SIGSEGV, Segmentation fault.
0x1c0e9ec3 in GC_find_limit ()
(gdb) bt
#0  0x1c0e9ec3 in GC_find_limit ()
#1  0x1c0e9d31 in GC_init_netbsd_elf ()
#2  0x1c0e9633 in GC_init_inner ()
#3  0x1c0e950f in GC_init ()
#4  0x1c09565f in scheme_set_stack_base ()
#5  0x1c003d0a in main ()

This problem persists regardless of whether mzscheme is built with - 
fno-stack-protector or not.

Any ideas? As far as I know, Matthew Flatt had it working on OpenBSD,  
so I imagine this is either something introduced recently, or messed  
up on my end.

-Patrick