ilc: Generate managed assembly references like upstream NativeAOT

[flibitijibibo]

Right now we just slap on an FNA.dll reference and hope that the rest of the program is monolithic:

https://github.com/FNA-XNA/NativeAOT-Xbox/blob/main/NativeAOT_Console.targets#L32

We need to dredge up the .targets files in mainline dotnet that somehow generate these references automatically. I'm pretty bad with msbuild myself so for now I've been recommending people update our targets file manually :(

[TheSpydog]

Submitted some instructions for this workflow in the meantime: f1cef1d