use UserHomeDir in stdmod lookup

stdmod.go

@@ -1,5 +1,10 @@
 package main
 
+import (
+	"os"
+	"path/filepath"
+)
+
 var stdmods = []string{
 	"os",
 }
@@ -15,8 +20,6 @@ func isstdmod(target string) bool {
 }
 
 func stdmoddir() string {
-	// todo: In Python, stdlib locates at "/usr/lib/python3.x".
-	// On distribution, the stdlib must be placed such directory and
-	// this must point there.
-	return "/home/hidetatz/shiba/std"
+	home, _ := os.UserHomeDir()
+	return filepath.Join(home, "shiba/std")
 }