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.
TamaGo is a bare metal runtime for unikernels, whose main use is a commercial product for secure USB keys, sold by F-Secure.
Back on my youth, writing compilers was considered systems programming, in parity with kernel drivers, how things change.
I guess writing userspace drivers in hybrid kernels is also not considered systems programming.
I guess the Genera, Xerox PARC, ETHZ, Microsoft folks are borderline dishonest.