fix: fix missed sourcemap content on cache key

Author: 3cp

lib/trace.js

@@ -38,7 +38,7 @@ module.exports = function(unit, opts = {}) {
       JSON.stringify(shim),
       depsFinder ? depsFinder.toString() : '',
       contents,
-      sourceMap
+      JSON.stringify(sourceMap)
     ].join('|');
     hash = generateHash(key);
     const cached = cache.getCache(hash);