cmd/ctrld: always pass config file on windows start mode

On windows, the SYSTEM user is used to run ctrld service. This user has
different environment with the user that run the `ctrld` binary via CLI.
That causes the mismatch issue in config file path, log path, or more
generally, everything that involve with home directory.

To circumvent this pain, just always passing the config path and the
original home dir in start mode. So `ctrld run` command can setup things
correctly.

cmd/ctrld/cli.go

@@ -144,6 +144,8 @@ func initCLI() {
 	runCmd.Flags().StringVarP(&logPath, "log", "", "", "path to log file")
 	runCmd.Flags().IntVarP(&cacheSize, "cache_size", "", 0, "Enable cache with size items")
 	runCmd.Flags().StringVarP(&cdUID, "cd", "", "", "Control D resolver uid")
+	runCmd.Flags().StringVarP(&homedir, "homedir", "", "", "")
+	_ = runCmd.Flags().MarkHidden("homedir")
 
 	rootCmd.AddCommand(runCmd)
 
@@ -169,14 +171,18 @@ func initCLI() {
 					defaultConfigFile = filepath.Join(dir, defaultConfigFile)
 					readConfigFile(true)
 				}
+				sc.Arguments = append(sc.Arguments, "--homedir="+dir)
+			}
 
-				// On Windows, the service will be run as SYSTEM, so if ctrld start as Admin,
-				// the written config won't be writable by SYSTEM account, we have to update
-				// the config here when "--cd" is supplied.
-				if runtime.GOOS == "windows" && cdUID != "" {
-					processCDFlags()
+			// On Windows, the service will be run as SYSTEM, so if ctrld start as Admin,
+			// the user home dir is different, so pass specific arguments that relevant here.
+			if runtime.GOOS == "windows" {
+				processCDFlags()
+				if configPath == "" {
+					sc.Arguments = append(sc.Arguments, "--config="+defaultConfigFile)
 				}
 			}
+
 			s, err := service.New(&prog{}, sc)
 			if err != nil {
 				stderrMsg(err.Error())

cmd/ctrld/main.go

@@ -22,6 +22,7 @@ var (
 	secondaryUpstream string
 	domains           []string
 	logPath           string
+	homedir           string
 	cacheSize         int
 	cfg               ctrld.Config
 	verbose           int
@@ -44,6 +45,9 @@ func normalizeLogFilePath(logFilePath string) string {
 	if logFilePath == "" || filepath.IsAbs(logFilePath) || service.Interactive() {
 		return logFilePath
 	}
+	if homedir != "" {
+		return filepath.Join(homedir, logFilePath)
+	}
 	dir, _ := os.UserHomeDir()
 	if dir == "" {
 		return logFilePath