Qt5WebKitWidgets not found?

I get this error, after following the 'Windows development build' of this manual (https://doc.owncloud.org/desktop/2.2/building.html):

Could not find a package configuration file provided by "Qt5WebKit" with
** any of the following names:**

** Qt5WebKitConfig.cmake**
** qt5webkit-config.cmake**

** Add the installation prefix of "Qt5WebKit" to CMAKE_PREFIX_PATH or set**
** "Qt5WebKit_DIR" to a directory containing one of the above files. If**
** "Qt5WebKit" provides a separate development package or SDK, be sure it has**
** been installed.**
Call Stack (most recent call first):
** src/CMakeLists.txt:8 (include)**

CMake Error at cmake/modules/QtVersionAbstraction.cmake:34 (message):
** Qt5WebKit required for Shibboleth. Use -DNO_SHIBBOLETH=1 to disable it.**
Call Stack (most recent call first):
** src/CMakeLists.txt:8 (include)**

-- Configuring incomplete, errors occurred!
See also "C:/git_clones/qtkeychain/CMakeFiles/CMakeOutput.log".
See also "C:/git_clones/qtkeychain/CMakeFiles/CMakeError.log".

If you don't use shibboleth, just try this cmake parameter (see log above)

Can explain yourself more? Don't know what 'DNO_SHIBBOLETH=1' means, and don't know why u suppose I don't use it.
Error.log sais:

Compiling the CXX compiler identification source file "CMakeCXXCompilerId.cpp" failed.
Compiler: cl
Build flags:
Id flags: -c

The output was:
System cannot find specified file

Checking whether the CXX compiler is IAR using "" did not match "IAR .+ Compiler":

And the output.log:

The system is: Windows - 10.0.10586 - AMD64