fix undef var

Author: kaaax0815

promise.js

@@ -1,7 +1,7 @@
 "use strict";
 
 const { load, currentTarget } = require("@neon-rs/load");
-const { familySync, GLIBC } = require("detect-libc");
+const { familySync, GLIBC, MUSL } = require("detect-libc");
 
 // Static requires for bundlers.
 if (0) {