Instead of patching configure, I added an additional line in the
${PKGDIR}/Makefile:

CONFIGURE_ENV+=         glib_cv_rtldglobal_broken=no

When using this updated package with my updates for gnucash 1.8.1 &
guile-1.6, I still get a coredump, but its further along than before:

athlon1k% gnucash
zsh: abort (core dumped)  gnucash
athlon1k% gdb /usr/pkg/bin/guile guile.core
[ snipped for brevity]
(gdb) bt
#0  0x48132337 in kill () from /usr/lib/libc.so.12
#1  0x4813446e in __libc_mutex_unlock () from /usr/lib/libc.so.12
#2  0x481a20aa in free () from /usr/lib/libc.so.12
#3  0x480ed0ef in tryall_dlopen_module () from
/usr/pkg/lib/libguile-ltdl.so.1
#4  0x480ed14c in find_module () from /usr/pkg/lib/libguile-ltdl.so.1
#5  0x480ee136 in try_dlopen () from /usr/pkg/lib/libguile-ltdl.so.1
#6  0x480ee587 in lt_dlopenext () from /usr/pkg/lib/libguile-ltdl.so.1
#7  0x480efd96 in scm_lt_dlopenext () from /usr/pkg/lib/libguile-ltdl.so.1
#8  0x4807a568 in sysdep_dynl_link () from /usr/pkg/lib/libguile.so.15
#9  0x4807a7b1 in scm_dynamic_link () from /usr/pkg/lib/libguile.so.15
#10 0x48085323 in scm_ceval () from /usr/pkg/lib/libguile.so.15
#11 0x480849fd in scm_ceval () from /usr/pkg/lib/libguile.so.15
#12 0x48086875 in scm_i_eval_x () from /usr/pkg/lib/libguile.so.15
#13 0x48086923 in scm_primitive_eval_x () from /usr/pkg/lib/libguile.so.15
#14 0x4809f321 in load () from /usr/pkg/lib/libguile.so.15
[ snipped ]
#80 0x8048e2c in dladdr ()
#81 0x4809d10e in invoke_main_func () from /usr/pkg/lib/libguile.so.15
#82 0x4809d0c3 in scm_boot_guile_1 () from /usr/pkg/lib/libguile.so.15
#83 0x4809cdd4 in scm_boot_guile () from /usr/pkg/lib/libguile.so.15
#84 0x8048e59 in main ()
#85 0x8048ad4 in ___start ()

full text is at http://www.elfin.net/netbsd/guile.core.txt

Ron