refine libexec

src/com/github/shadowsocks/ShadowsocksApplication.java

@@ -1,13 +1,21 @@
 package com.github.shadowsocks;
 
 import android.app.Application;
+import android.content.Context;
 import com.google.analytics.tracking.android.EasyTracker;
 
 public class ShadowsocksApplication extends Application {
 
+    private static String sTmpDir;
+
+    public static String getTmpDir() {
+        return sTmpDir;
+    }
+
     @Override
     public void onCreate() {
         EasyTracker.getInstance().setContext(this);
+        sTmpDir = getCacheDir().getAbsolutePath();
     }
 
 }