How to use Eigen for PX4 AutoPilot


I’m trying to implement a lqr controller.
As the system matrix varies over time, I have to calculate lqr gain after solving a continuous time algebraic riccati equation every timestep.
To do this, I need Eigen especially for Eigen::FullPivLU.
But when I build the PX4 Autopilot code with “make px4_fmu-v2_default”, I get below error

/usr/include/eigen3/Eigen/Core:96:10: fatal error: complex: No such file or directory

I heard that I can’t use standard cpp library for nuttx which seems to be the cause of the problem.
Is there any way to use Eigen in PX4 Autopilot?

Thank you.