Want to build a porate box using LeMaker™ Guitar

LeMaker™ Guitar Key features
● Quad-core ARM® Cortex™-A9R4 CPU;
● System on module design;
● 1GB/2GB DDR3 SDRAM;
● On-board 8GB eMMC NAND flash storage;
● 204 pins standard DDR3 SODIMM for connecting LeMaker™ Guitar base board;
● Hardware ADFU button;
● Android 5.0 and Linux support.

LeMaker™ Guitar Base Board Rev.B Key features
● 1 x micro-B USB3.0 receptacle and 2 x type-A USB2.0 receptacle;
● Wi-Fi 802.11 b/g/n 2.4GHz and Bluetooth 4.0;
● 10/100Mbps RJ45 ethernet;
● HDMI type-A and LVDS display interface;
● 40 pins expansion compatible with Raspberry Pi 2;
● 204 pins standard DDR3 SODIMM connector for connecting LeMaker Guitar.

I want to build a pirate box based on the above board with the specifications
please help me how we can build a OS img for the LeMaker Guitar

You can take a look at the RPi repo [github.com] and how we do it there.
If you find an arch rootfs for your platform, you can simply change that in the build chain and you are good to go.