Windows
The Qt-Nacl is not support, for now, in Windows.
By the way, here is the github repository dedicated for it -> https://github.com/msorvig/qt5-qtbase-nacl
In the file nacl-readme it is written :
[...] Windows is not supported as a host platform.
Linux
If you want to compile in Linux, I have made a script that will compile Qt5.4 with NaCl with all the dependencies needed.
https://gist.github.com/theshadowx/438297ac465874a5e226
I also made a video that will show the different steps and a showCase at the end :