Fortran
The Fortran front-end for gcc can be enabled by adding pkgs.gfortran.cc to environment.systemPackages. [1]
The addition of .cc indicates the compiler itself without the gcc-wrapper Nix expressions used by gfortran. [2]
If both gcc and gfortran (without .cc) are included, the build may fail with an error of the form: "collision between gfortran-wrapper/bin/gcc and gcc-wrapper/bin/gcc".