Fix compile errors

Signed-off-by: cyy <[email protected]>

Author: cyyever

kernels/portable/cpu/op_native_dropout.cpp

@@ -9,6 +9,7 @@
 #include <executorch/kernels/portable/cpu/util/elementwise_util.h>
 #include <executorch/runtime/kernel/kernel_includes.h>
 
+#include <optional>
 #include <random>
 #include <tuple>
 
@@ -17,7 +18,7 @@ std::tuple<Tensor&, Tensor&> native_dropout_out(
     KernelRuntimeContext& ctx,
     const Tensor& input,
     double prob,
-    torch::executor::std::optional<bool> train,
+    ::std::optional<bool> train,
     Tensor& out,
     Tensor& mask) {
   std::tuple<Tensor&, Tensor&> ret(out, mask);