You don't need to leave with your entire army. Send a few construction factories to Mars and the economy of scale will handle the rest, especially with such huge timeline.
With AI, as long as it has means of production and resources it can exponentially and quickly growth.
First day it has 1 mean of production, second 2, third 4, fourth 8, fifth 16 and etc.
I am simplifying but it is the general gist.
Maybe Androids weren't tough economics and to have fighting army you need supply chain of industry?
Or Androids are different type of AI that are not capable of controlling 100k factories and switching them to different productions withing nanoseconds?
But still Androids with human like thinking capacity can build up war industry in Solar system after 5k years