To reproduce:
1) Open attached project
2) Make sure either Test scene is open or added to build order
3) Build for WebGL

Expected: The project builds
Actual: It freezes (in older versions, on compiling native JS, in 5.5, on 'Converting managed assemblies to C++';, in 5.6 and 2017.1 it was yet another note. However, in all of them when checking the whole progress in Process Explorer, it always freezes when reaching node.exe )

Reproduced in 5.3.5f1, 5.4.5f1, 5.5.2p1, 5.6.0b11, 2017.1.0a2