Build Lightning Freezes UE 4.12

Please help me!!! When I click “Build lightning only” or just “Build” it freezes the UE4! I’ve checked the SwarmAgent and it gives me this error:

And here’s the picture of UE4 freeze:

Please help me, I’m just a student who really love UE4 :’(
And sorry for my bad English, though. I’m from Vietnam.

My Specs:

CPU:Core i3 6100 3.7ghz

GPU: NVIDIA GTX 950

Ram: Avexir 8gb 2400mhz

HDD: Seagate 1TB