linker problem blocking qt5 update

[Mark Davies <mark%ecs.vuw.ac.nz@localhost>]

I'd like to update the qt5 in pkgsrc to the 5.10.0 version that is
currently in pkgsrc-wip.  However there is a problem for me on at least
NetBSD-7*/amd64 and NetBSD-8*/amd64, that many packages that want to
link against libQt5Widgets fail with this error:

ld: BFD (NetBSD Binutils nb1) 2.27 assertion fail
/usr/src/external/gpl3/binutils/lib/libbfd/../../dist/bfd/elflink.c:2694
ld: BFD (NetBSD Binutils nb1) 2.27 assertion fail
/usr/src/external/gpl3/binutils/lib/libbfd/../../dist/bfd/elflink.c:2694

It does however work fine for me on linux and I have been told that it
works on NetBSD with clang.

I've just committed wip/phonon-qt5 to demonstrate the problem. On NetBSD
8.0_BETA/amd64 with the system gcc the build of this package fails with:

[ 51%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/audiooutputadaptor.cpp.o
[ 52%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/phonon4qt5_autogen/mocs_compilation.cpp.o
[ 54%] Linking CXX shared library libphonon4qt5.so
ld: BFD (NetBSD Binutils nb1) 2.27 assertion fail
/usr/src/external/gpl3/binutils/lib/libbfd/../../dist/bfd/elflink.c:2694
ld: BFD (NetBSD Binutils nb1) 2.27 assertion fail
/usr/src/external/gpl3/binutils/lib/libbfd/../../dist/bfd/elflink.c:2694
phonon/CMakeFiles/phonon4qt5.dir/build.make:1004: recipe for target
'phonon/libphonon4qt5.so.4.9.1' failed
gmake[2]: *** [phonon/libphonon4qt5.so.4.9.1] Error 1

This bug has been blocking an update of the qt5 packages for some time
(and those packages that require a newer qt5).

It would be useful to know the result of building the wip/phonon-qt5
package for other people and on different platforms/compilers.

And if someone could actually describe what this is actually complaining
about and how to fix it, that would be brilliant.

cheers
mark