syscall: add more stubs as needed for Go 1.20 support

src/syscall/syscall_unix.go

@@ -1,3 +1,18 @@
 package syscall
 
 func Exec(argv0 string, argv []string, envv []string) (err error)
+
+// The two SockaddrInet* structs have been copied from the Go source tree.
+
+type SockaddrInet4 struct {
+	Port int
+	Addr [4]byte
+	raw  RawSockaddrInet4
+}
+
+type SockaddrInet6 struct {
+	Port   int
+	ZoneId uint32
+	Addr   [16]byte
+	raw    RawSockaddrInet6
+}