It depends. Someone more experienced may be able to add more info, but gyp appears to know what is available pre-built vs what needs to be built. Depending on w

It depends. Someone more experienced may be able to add more info, but gyp appears to know what is available pre-built vs what needs to be built. Depending on what platform and options you've selected it might call (for example) the Visual Studio C compiler to build a native extension for you.