qt5 missing symbol problem

[Niclas Rosenvik <nros%NetBSD.org@localhost>]

Hi pkgsrc-users, I have been trying update qt5 to version 5.5 in pkgsrc.
I have come across a problem I can't solve. qt5-qtdoc uses
qhelpgenerator from qt5-qttools and it can't start because it can't
dlopen ${PREFIX}/plugins/platforms/libqminimal.so.
when testing to dlopen this file with a homemade program I get this
message from dlerror:
/usr/pkg/qt5/lib/libQt5PlatformSupport.so: Undefined symbol
"_ZTV21QDeviceDiscoveryDummy" (symnum = 52)

QDeviceDiscoveryDummy is defined in 
src/platformsupport/devicediscovery/qdevicediscovery_dummy.cpp

I have tried to add this function to a dynamic list and also tried to
use -E linker argument to no avail.

libQt5Platformsupport.so from version 5.4 dlopens without a problem.

Anybody who knows how to solve this problem?

Thanks in advance,
Niclas Rosenvik