[Windows] Building with GUI fails

[AnotherFoxGuy]

Building the current master on windows with GUI enabled fails with:

f:\ror-server\source\server\master-server.h(23): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\master-server.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\config.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\broadcaster.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\messaging.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\listener.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\rorserver.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\receiver.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\ScriptEngine.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\sequencer.cpp)
f:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\server\userauth.cpp)
F:\ror-server\source\server\sequencer.h(28): fatal error C1083: Cannot open include file: 'json/json.h': No such file or directory (compiling source file F:\ror-server\source\gui\servergui.cpp)

[ohlidalp]

Hmm, something's wrong with JsonCpp. It used to be a GUI/webserver dependency, but now it's a core dependency.

Please try finding which commit broke it, start with the one where I changed JsonCpp in CMake-files.