ci: bump ubuntu from 16.04 to 18.04
ci: bump ubuntu from 16.04 to 18.04

raulgrell/zig,zig-lang/zig,raulgrell/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,andrewrk/zig,andrewrk/zig,raulgrell/zig,zig-lang/zig