Neon related building errors on ARM aarch64 when using Castxml

The main problem noticed when building ITK with CastXML support is described here: https://github.com/InsightSoftwareConsortium/ITK/issues/1959. The part where Eigen comes in is described in the comment here: https://github.com/InsightSoftwareConsortium/ITK/issues/1959#issuecomment-681959157. Basically the CastXML developers suggest Eigen should handle CastXML in the same way it does Clang (the latter requires workarounds due to issue #1325 (closed)); for example

 // See bug 1325, clang fails to call vld1q_u64.
-#if EIGEN_COMP_CLANG
+#if EIGEN_COMP_CLANG || defined(__castxml__)

in Eigen/src/Core/arch/NEON/Complex.h Line#293.

Thanks.