Can't build for Windows

with github.musescore-musescore-1dff0380 the error changed slightly:

Linking CXX executable mscore.exe
CMakeFiles\mscore.dir/objects.a(palette.cpp.obj): In function `ZNK2Ms9XmlReader9attributeEPKc':
.../MuseScore/libmscore/xml.h:69: undefined reference to `_imp___ZNK19XmlStreamAttributes5valueERK7QString'
CMakeFiles\mscore.dir/objects.a(palette.cpp.obj): In function `ZN7QVectorI18XmlStreamAttributeE8destructEPS0_S2_':
C:/Qt/5.2.1/mingw48_32/include/QtCore/qvector.h:292: undefined reference to `_imp___ZN18XmlStreamAttributeD1Ev'
..\libmscore\liblibmscore.a(xml.cpp.obj): In function `ZNK2Ms9XmlReader12intAttributeEPKci':
.../MuseScore/libmscore/xml.cpp:33: undefined reference to `_imp___ZNK19XmlStreamAttributes5valueERK7QString'
..\libmscore\liblibmscore.a(xml.cpp.obj): In function `ZNK2Ms9XmlReader12intAttributeEPKc':
.../MuseScore/libmscore/xml.cpp:40: undefined reference to `_imp___ZNK19XmlStreamAttributes5valueERK7QString'
..\libmscore\liblibmscore.a(xml.cpp.obj): In function `ZNK2Ms9XmlReader15doubleAttributeEPKc':
.../MuseScore/libmscore/xml.cpp:49: undefined reference to `_imp___ZNK19XmlStreamAttributes5valueERK7QString'
..\libmscore\liblibmscore.a(xml.cpp.obj): In function `ZNK2Ms9XmlReader15doubleAttributeEPKcd':
.../libmscore/xml.cpp:55: undefined reference to `_imp___ZNK19XmlStreamAttributes5valueERK7QString'
..\libmscore\liblibmscore.a(xml.cpp.obj): In function `ZNK2Ms9XmlReader9attributeEPKcRK7QString':
.../MuseScore/libmscore/xml.cpp:67: undefined reference to `_imp___ZNK19XmlStreamAttributes5valueERK7QString'
..\libmscore\liblibmscore.a(xml.cpp.obj):C.../MuseScore/thirdparty/xmlstream/xmlstream.h:120: more undefined references to `_imp___ZNK19XmlStreamAttributes5valueERK7QString' follow
..\libmscore\liblibmscore.a(xml.cpp.obj): In function `ZN7QVectorI18XmlStreamAttributeE11reallocDataEii6QFlagsIN10QArrayData16AllocationOptionEE':
C:/Qt/5.2.1/mingw48_32/include/QtCore/qvector.h:482: undefined reference to `_imp___ZN18XmlStreamAttributeC1ERKS_'
..\libmscore\liblibmscore.a(xml.cpp.obj): In function `ZN7QVectorI18XmlStreamAttributeE16defaultConstructEPS0_S2_':
C:/Qt/5.2.1/mingw48_32/include/QtCore/qvector.h:265: undefined reference to `_imp___ZN18XmlStreamAttributeC1Ev'
..\thirdparty\xmlstream\libxmlstream.a(xmlstream.cpp.obj): In function `ZN23XmlStreamEntityResolverD2Ev':
.../MuseScore/thirdparty/xmlstream/xmlstream.cpp:175: undefined reference to `_imp___ZTV23XmlStreamEntityResolver'
collect2.exe: error: ld returned 1 exit status
mscore\CMakeFiles\mscore.dir\build.make:8267: recipe for target 'mscore/mscore.exe' failed
CMakeFiles\Makefile2:266: recipe for target 'mscore/CMakeFiles/mscore.dir/all' failed
makefile:135: recipe for target 'all' failed
mingw32-make[2]: *** [mscore/mscore.exe] Error 1
mingw32-make[1]: *** [mscore/CMakeFiles/mscore.dir/all] Error 2
mingw32-make: *** [all] Error 2

setting VERBOSE=1 additionally shows:
Linking CXX executable mscore.exe
cd /d C:\Users\joschmitz\Documents\GitHub\MuseScore\build.qtc\mscore && "C:\Program Files (x86)\CMake 2.8\bin\cmake.exe" -E cmake_link_script CMakeFiles\mscore.dir\link.txt --verbose=1
"C:\Program Files (x86)\CMake 2.8\bin\cmake.exe" -E remove -f CMakeFiles\mscore.dir/objects.a
C:\Qt\Tools\mingw48_32\bin\ar.exe cr CMakeFiles\mscore.dir/objects.a @CMakeFiles\mscore.dir\objects1.rsp
C:\Qt\Tools\mingw48_32\bin\g++.exe -std=gnu++0x -mno-ms-bitfields -g .../MuseScore/build.qtc/resfile.o -mwindows -mconsole -L C:/Qt/5.2.1/mingw48_32/lib -Wl,--whole-archive CMakeFiles\mscore.dir/objects.a -Wl,--no-whole-archive -o mscore.exe -Wl,--out-implib,libmscore.dll.a -Wl,--major-image-version,0,--minor-image-version,0 ..\awl\libawl.a ..\mstyle\libmstyle.a ..\thirdparty\diff\libdiff_match_patch.a ..\bww2mxml\libbww.a ..\thirdparty\rtf2html\librtf2html.a ..\thirdparty\singleapp\src\libqtsingleapp.a ..\synthesizer\libsynthesizer.a ..\midi\libmidi.a ..\fluid\libfluid.a ..\effects\libeffects.a -lvorbisfile ..\libmscore\liblibmscore.a ..\thirdparty\xmlstream\libxmlstream.a ..\thirdparty\qzip\libqzip.a ..\zerberus\libzerberus.a ..\synthesizer\libsynthesizer.a ..\aeolus\libaeolus.a -lvorbis -logg ..\audiofile\libaudiofile.a -lsndfile-1 ..\thirdparty\ofqf\libofqf.a -lportaudio ..\thirdparty\portmidi\libportmidi.a -lwinmm -lz -lQt5Svg -lQt5Gui -lQt5Core -lQt5Widgets -lQt5Xml -lQt5Network -lQt5WebKitWidgets -lQt5WebKit -lQt5XmlPatterns -lQt5PrintSupport -lQt5Quick -lQt5Qml -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32

It seems to have to do with linking dynamic vs. static.
Before the move these had been compiled and linked statically, they are still build as a static lib after the move, but tried to get linked dynamically (as a dll)

See https://www.google.de/#q=undefined+reference+to+%60_imp_

Got it (I think)! See PR #892
Got rid of the linker errors, but also of a whole bunch of warnings that were annoying me since a while.
So here's proof for my Mantra: "Warnings Are Evil" esp. if you don't understand them. And they are also evil if you do understan them, but that are many, as it is way too easy to miss the tree in the forest...

Hmm, well, still some warnings left:
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:67:6: warning: 'static bool QXmlUtils::rangeContains(QXmlUtils::RangeIter, QXmlUtils::RangeIter, QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::rangeContains(RangeIter begin, RangeIter end, const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:157:6: warning: 'static bool QXmlUtils::isIdeographic(QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isIdeographic(const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:186:6: warning: 'static bool QXmlUtils::isCombiningChar(QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isCombiningChar(const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:200:6: warning: 'static bool QXmlUtils::isDigit(QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isDigit(const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:214:6: warning: 'static bool QXmlUtils::isExtender(QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isExtender(const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:219:6: warning: 'static bool QXmlUtils::isBaseChar(QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isBaseChar(const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:233:6: warning: 'static bool QXmlUtils::isEncName(const QString&)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isEncName(const QString &encName)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:254:6: warning: 'static bool QXmlUtils::isLetter(QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isLetter(const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:268:6: warning: 'static bool QXmlUtils::isChar(QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isChar(const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:287:6: warning: 'static bool QXmlUtils::isNameChar(QChar)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isNameChar(const QChar c)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:310:6: warning: 'static bool QXmlUtils::isPublicID(const QString&)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
bool QXmlUtils::isPublicID(const QString &candidate)
^
...\MuseScore\thirdparty\xmlstream\xmlutils.cpp:369:6: warning: 'static bool QXmlUtils::isNCName(const QStringRef&)' redeclared without dllimport attribute after being referenced with dll linkage [enabled by default]
bool QXmlUtils::isNCName(const QStringRef &ncName)

Seems in xmlutils_p.h another Q_CORE_EXPORT needs to get deleted, sorry I missed it in the first round (QtCreator doesn't show it!?!), PR to follow shortly

And there is still:
...\MuseScore\thirdparty\ofqf\qosctypes.cpp: In member function 'void PathObject::signalData(QVariant)':
...\MuseScore\thirdparty\ofqf\qosctypes.cpp:153:52: warning: comparison between 'enum QVariant::Type' and 'enum QMetaType::Type' [-Wenum-compare]
if ( v.type() == _type || (v.type() == QMetaType::Float && _type == QVariant::Double) ) {
...
...\MuseScore\mscore\ove.cpp: In function 'bool OVE::getMiddleUnit(OVE::OveSong*, int, int, OVE::Measure*, OVE::Measure*, int, int, OVE::Measure*, int&)':
...\GitHub\MuseScore\mscore\ove.cpp:7636:6: warning: parameter 'middleMeasure' set but not used [-Wunused-but-set-parameter]
bool getMiddleUnit(
^

Not sure what to do about these, I guess the 1st needs a cast and the 2nd may need a change from pointer to reference?

See PR #893