[plt-scheme] mzscheme x86-64 doesn't build

Problems with linking unwind?
gcc-4.1.2, GNU/Linux-amd64, svn 12687
$ make
...
gcc -o .libs/mzschemecgc .libs/main.o -rdynamic  ./.libs/libmzscheme.so 
./.libs/libmzgc.so -ldl -lm  -Wl,--rpath -Wl,/usr/local/plt/lib
./.libs/libmzscheme.so: undefined reference to `unw_get_ip'
./.libs/libmzscheme.so: undefined reference to `unw_get_frame_pointer'
./.libs/libmzscheme.so: undefined reference to `unw_reset_bad_ptr_flag'
./.libs/libmzscheme.so: undefined reference to `_ULx86_64_step'
./.libs/libmzscheme.so: undefined reference to `unw_manual_step'
./.libs/libmzscheme.so: undefined reference to 
`unw_set_safe_pointer_range'
./.libs/libmzscheme.so: undefined reference to `_ULx86_64_init_local'
collect2: ld returned 1 exit status
make[4]: *** [mzschemecgc] Error 1
make[4]: Leaving directory `/usr/local/src/plt-svn/plt/src/mzscheme'
make[3]: *** [cgc] Error 2
make[3]: Leaving directory `/usr/local/src/plt-svn/plt/src/mzscheme'
make[2]: *** [3m] Error 2
make[2]: Leaving directory `/usr/local/src/plt-svn/plt/src/mzscheme'
make[1]: *** [3m] Error 2
make[1]: Leaving directory `/usr/local/src/plt-svn/plt/src'
make: *** [all] Error 2

-- vyzo