include netinet/in.h in src/nix/main.cc

Fixes #3186

src/nix/main.cc

@@ -15,6 +15,7 @@
 #include <sys/socket.h>
 #include <ifaddrs.h>
 #include <netdb.h>
+#include <netinet/in.h>
 
 extern std::string chrootHelperName;