In my prior comments above and in all the following I use "language" in the typical way, which is to say referring to not just the syntax but the semantics of the standard toolchain and runtime as well. I wanted to clarify that since perhaps there is some confusion there. So when I talk about Go I'm talking about what I get here[1] as is everyone else who isn't explicitly specifying some other implementation.
Writing compilers is not systems programming in the sense that it requires a systems programming language, no. One could easily write a C compiler in Ruby, but we don't consider Ruby to be a systems programming language.
Thus, obviously, Go, despite not being a systems programming language, could be used to write the compiler for a systems programming language. I guess that is what Tamago is? I'm not going to read through the source to find out and the web page you linked is boring marketing copy.