openjdk8 missing /usr/pkg/gcc6/x86_64--netbsd/lib RPATH when built with gcc-6.4

[David Brownlee <abs%absd.org@localhost>]

Since netbsd-8 has to pull in gcc-6 in order to build firefox I
thought I'd try building a few other packages with gcc-6 to see if
anything exploded.

One detonater was openjdk8, which fails with

Error: failed /usr/pkg/java/openjdk8/jre/lib/amd64/server/libjvm.so,
because /usr/lib/libstdc++.so.7: version CXXABI_1.3 required by
/usr/pkg/java/openjdk8/jre/lib/amd64/server/libjvm.so not defined

# ldd /usr/pkg/java/openjdk8/jre/lib/amd64/server/libjvm.so
/usr/pkg/java/openjdk8/jre/lib/amd64/server/libjvm.so:
        -lstdc++.7 => /usr/lib/libstdc++.so.7

Setting "export LD_LIBRARY_PATH=/usr/pkg/gcc6/x86_64--netbsd/lib"
allows everything to work

Would anyone have any ideas on how to approach fixing this :)

Thanks

David