Address comments

Author: larryliu0820

backends/qualcomm/CMakeLists.txt

@@ -64,7 +64,9 @@ if(EXECUTORCH_BUILD_PYBIND)
     )
   endif()
   set(ENV{QNN_SDK_ROOT} ${QNN_SDK_ROOT})
-elseif(NOT DEFINED QNN_SDK_ROOT)
+endif()
+
+if(NOT DEFINED QNN_SDK_ROOT)
   message(
     FATAL_ERROR
       "Please define QNN_SDK_ROOT, e.g. cmake <..> -DQNN_SDK_ROOT=<...>"