libstdc++.so: undefined reference to `_Unwind_GetIPInfo@GCC_4.2.0' (octave on netbsd-7)

[coypu%SDF.ORG@localhost]

Hi,

Builds of math/octave on netbsd-7 have been failing for a while,
with the failure being:

/usr/lib/libstdc++.so: undefined reference to `_Unwind_GetIPInfo@GCC_4.2.0'
Makefile:2308: recipe for target 'octave-gui' failed
gmake[2]: *** [octave-gui] Error 1

(full log at http://ftp.netbsd.org/pub/pkgsrc/misc/joerg/20161116.1045/octave-4.0.3nb2/build.log
warning: giant file)

octave is an interesting package because the defaults on pkgsrc mean
it uses g95 (which is gcc 4.1), and qt5 with its C++?? insanity.

the weird thing is that _Unwind_GetIPInfo@GCC_4.2.0 really
isn't defined anywhere in netbsd-6/7*. It's just undefined for
libstdc++.so. How are other things not hitting this error?

Thanks.

* I actually only checked netbsd-6.