Fix: Guard C++17 ellint derivatives to fix CI build on older standards

Author: ayush4874

include/clad/Differentiator/BuiltinDerivatives.h

@@ -1062,6 +1062,8 @@ CUDA_HOST_DEVICE void hypot_pullback(T x, T y, U d_z, T* d_x, T* d_y) {
   *d_y += (y / h) * d_z;
 }
 
+#if __cplusplus >= 201703L
+
 template <typename T, typename dT>
 CUDA_HOST_DEVICE ValueAndPushforward<T, dT> comp_ellint_1_pushforward(T k, dT d_k) {
   T K = ::std::comp_ellint_1(k);
@@ -1111,6 +1113,8 @@ CUDA_HOST_DEVICE ValueAndPushforward<T, dT> comp_ellint_3_pushforward(T k, U nu,
 
   return {result, d_result};
 }
+
+#endif
 } // namespace std
 
 CUDA_HOST_DEVICE inline ValueAndPushforward<float, float>
@@ -1375,9 +1379,11 @@ using std::min_pushforward;
 using std::pow_pullback;
 using std::pow_pushforward;
 using std::sqrt_pushforward;
+#if __cplusplus >= 201703L
 using std::comp_ellint_1_pushforward;
 using std::comp_ellint_2_pushforward;
 using std::comp_ellint_3_pushforward;
+#endif
 
 namespace class_functions {
 template <typename T, typename U>