cross-platform clean, and fix windows build

.gitignore

@@ -30,3 +30,4 @@ src/*/*.js
 src/*.js
 dist
 /package-lock.json
+/yarn.lock

clean.js

@@ -0,0 +1,21 @@
+const path = require("path");
+const fs = require("fs");
+function walk(dir) {
+  var results = [];
+  var list = fs.readdirSync(dir);
+  list.forEach(function(file) {
+    file = path.join(dir, file);
+    var stat = fs.statSync(file);
+    if (stat && stat.isDirectory()) {
+      results = results.concat(walk(file));
+    } else {
+      // 过滤后缀名（可按你需求进行新增）
+      if (path.extname(file) === ".js") {
+        results.push(path.resolve(__dirname, file));
+      }
+    }
+  });
+  return results;
+}
+
+walk(path.join(__dirname, "src")).forEach(file => fs.unlinkSync(file));