packager: GlobalTransformCache: fix non-bound function

Reviewed By: cpojer

Differential Revision: D4972905

fbshipit-source-id: c9aaaba47f2c74bf48b7cbbc1255992d36ae32b1

packager/src/lib/GlobalTransformCache.js

@@ -408,8 +408,9 @@ class OptionsHasher {
   }
 
   relativizeFilePaths(filePaths: Array<string>): Array<string> {
-    return filePaths.map(this.relativizeFilePath);
+    return filePaths.map(this.relativizeFilePath.bind(this));
   }
+
   relativizeFilePath(filePath: string): string {
     return path.relative(this._rootPath, filePath);
   }