Building should be simple just need that Grass7 API, VS2015 recommended. Place into system32 of target OS and config .gr7updpkg files to launch with it. Also, you will need bit7z library and you will need to install it in "C:\bit7z".
I needed a way of updating releases of Grass7 without making huge ass ISOs.
This version does NOT work with the update files i release due to security reasons.