Halfway decent GCC suite for NixOS, I think

gcc-suite15 = pkgs.wrapCC (
    pkgs.gnat14.cc.override {
      name = "gcc-suite15";
      langAda = true;
      langC = true;
      langCC = true;
      #langD = true;
      langFortran = true;
      langGo = true;
      langJit = true;
      langObjC = true;
      langObjCpp = true;
      #langRust = true;
      profiledCompiler = true;
      reproducibleBuild = false;
      majorMinorVersion = "15";
      isl = pkgs.isl_0_24;
      gmp = pkgs.gmp6;
      mpfr = pkgs.mpfr;
      libmpc = pkgs.libmpc;
      zlib = pkgs.zlib;
      gnused = pkgs.gnused;
    }
  );