How to find out GCC -march and -mtune options on installed lubuntu?

I am trying to run yocto warrior image on my device. A device has following configuration:

Chipset Architecture : Intel NM10 express
OS : Yocto warrior
CPU : Atom D2250 Dual Core
Volatile Memory : 2GB DDR3
CPU core : 4

I am facing issues with 64-bit yocto image to get it working on device but lubuntu(19.10 Eoan Ermine) is running as expected on same device.

My question is, How do I determine GCC -march and -mtune options on already installed lubuntu?

This will help me to compare options/flags provided to GCC for yocto and lubuntu.

Thanks in Advance !