Created attachment 775224 [details] emerge --info '=dev-dotnet/gtk-sharp-2.99.3-r1::dotnet fails to build because of two reasons, I attached a patch that resolves it
Created attachment 775227 [details] emerge -pqv '=dev-dotnet/gtk-sharp-2.99.3-r1::dotnet
Created attachment 775230 [details] build.log of first problem
Created attachment 775233 [details, diff] build.log of second problem
Created attachment 775236 [details] build.log of second problem
Created attachment 775239 [details, diff] patch that fixes both problems