Qt5Network.lib(Qt5Network.dll) : fatal error LNK1112: module machine type 'x64' conflicts with target machine type 'X86'

$> nmake
(...)
moc_webfile.cpp
moc_xmlparser.cpp
moc_QBreakpadHandler.cpp
moc_QBreakpadHttpUploader.cpp
Generating Code...
 link /NOLOGO /DYNAMICBASE /NXCOMPAT /INCREMENTAL:NO /SUBSYSTEM:WINDOWS "
/MANIFESTDEPENDENCY:type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0'
 publicKeyToken='6595b64144ccf1df' language='*' processorArchitecture
='*'" /VERSION:1.21 /MANIFEST:embed /OUT:"release\Haivision Helper.exe" @C:\Users\Frank\AppData\Local\Temp\nmD970.tmp
Qt5Network.lib(Qt5Network.dll) : fatal error LNK1112: module machine type 'x64' conflicts with target machine type 'X86'
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\BIN\link.EXE"' : return code '0x458'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\BIN\nmake.exe"' : return code '0x2'
Stop.