refactor: restrict kgg db support to Windows only

algo/kgm/pc_kugou_db/cipher_default.go

@@ -0,0 +1,7 @@
+//go:build !windows
+
+package pc_kugou_db
+
+func CachedDumpEKey(dbPath string) (map[string]string, error) {
+	return nil, nil
+}