build with netgo tag to make the executable static
build with netgo tag to make the executable static

fix https://github.com/NebulousLabs/Sia/issues/2007

NebulousLabs/Sia,mharkus/Sia,ChrisSchinnerl/Sia,mtlynch/Sia,NebulousLabs/Sia,ChrisSchinnerl/Sia,mtlynch/Sia,ericflo/Sia,ericflo/Sia,mharkus/Sia