Resolvido
Encontrei uma solução para um problema relatado semelhante ao meu, aqui neste link:
http://qt-project.org/forums/viewthread/18329
Ao aplicar a solução sugerida, consegui compilar a Qt e em seguida compilei meu aplicativos sem problema:
For gosh sake…answer the OP’s question!
Add -fno-keep-inline-dllexport to the mkspec file for win32-g++. It should be located somewhere like:
C:\Qt\4.8.3\mkspecs\win32-g++\qmake.conf
Look for a variable called QMAKE_CXXFLAGS and add it there.
A pessoa que sugeriu a solução não da nenhuma explicação do porque do erro, apesar da solução funcionar, aqui neste outro link encontrei algumas explicações:
http://sourceforge.net/mailarchive/message.php?msg_id=28485608
ld memory usage: because of the way import libraries are handled, it
turns out that linking "directly to the DLL" is both much faster and
uses much less memory. However, it only works if (a) the DLL exports no
DATA symbols, and (b) the "implib" has no externally added "static"
members (libcygwin.a and libmsys-1.0.a are the import libs for
cygwin-1.dll and msys-1.0.dll respectively, and they are both very odd
because they add additional static .o's to the implib).
IF you are sure that your dll satisfies these requirements, then you can
TRY simply copying /bin/foo.dll onto /lib/libfoo.dll.a.
If you need to do this for "curretly built" dlls in your source tree,
obviously you'd need to munge up your Makefile.am/Makefile.in to add the
new 'cp' rules. Libtool, if used, will make things difficult but it can
be done.
A outra parte da minha duvida, sobre qual versão do Mingw usar, também foi resolvida, compilou a Qt com a ultima versão disponível do Mingw em seu site.
