Thanks!Shouldn't have to do that. That means that you are probably not in the mingw64 shell since it should be set up with /mingw64/bin in the path already (that or your mingw64 shell is borked.)
-DMINGW_STATIC_BUILD=1 is fine as well, it just has to be non zero. I'll update the wiki then since its a little misleading
Do you still have the non static qt5 installed? If so, i'm guessing cmake is finding the non static QT5 instead of the static one, so it can't link. Check the CMakeCache to see what the Qt5_DIR variable is, If its not the directory to qt5-static then you need to explicitly set the Qt5_DIR to the location of qt5-static instead. ( -DQt5_DIR=/path/to/qt5-static )
In fact it was using the non-static QT libraries...
And about the path problem, I was in the Mingw64 shell, but I supose this is a problem caused by installing msys2 in a different folder than C:\. I installed it on my 2nd HDD D:\ (these shells are very anoying with path matters...).