Fix qualcomm backend build failure

Signed-off-by: Jie Fu <[email protected]>

Author: DamonFool

backends/qualcomm/runtime/backends/QnnOpPackageManager.h

@@ -8,6 +8,7 @@
 #pragma once
 #include <mutex>
 #include <unordered_set>
+#include <string>
 
 namespace executorch {
 namespace backends {