Ooopsy. What a crap I wrote about Sphereworlds!
I just thought you had asked about sphereworlds. Sorry.
Well, the right answer will be "I don't know".
Or follow the advice that Rag-X gave, add a Cargo Storage ability to Spaceports. To make such facility a "homeworld only", create racial facilities with Spaceport and Cargo storage abilities and make them very expensive. Although you'll have to test which facility will be placed on a HW: generic SP or racial one.
edit: Resupply Depot is another convenient facility.
edit2: actualy, resupply depot is better, because Natural Merchants trait will remove Space Port from HW.
edit3: on a second thought AI will likely prefere to build expensive racial resupply depot or Space port in just colonised systems. It can cause AI to stumble and waste its resourses on a very expensive facilities. If you want to go further - add an AI tag to resupply depot (or space port) and change all AI_construction_facilities.txt to reflect this change.
edit4: never mind