I am using imx8mn board. I had a working Android boot img running. I made changes and redid the booting. I am working on Ubuntu 16.04 which is part of a dual booted PC. The allocated memory for the linux machine is 200+ GB. After remaking the kernel and boot images. My Ubuntu has run out of space. The main bulk of the memory is being used by .intermediate folder in <directory>/out/soong/.intermediate
The android BSP is not tested on ubuntu 16 you can try ubuntu 18, and it takes aprox 150GB, do not know exactly why it takes too much in your computer but you must deleted everything before compiled again.
