switch to s6-linux-init and s6-rc

This is at the point where it runs a getty and a pile of s6-supervise
processes, though it doesn't seem to run the things being supervised

tests/pseudofiles/structure.nix

@@ -0,0 +1,45 @@
+let
+  dir = contents: { type = "d"; inherit contents; };
+  structure = {
+    service = dir {
+      s6-linux-init-runleveld = dir {
+        notification-fd = { file = "3"; };
+        run = {
+          file = ''
+           hello
+           world
+          '';
+          mode = "0755";
+        };
+      };
+      s6-linux-init-shutdownd = dir {
+        fifo = {
+          type = "i";
+          subtype = "f";
+          mode = "0600";
+        };
+        run = {
+          file = ''
+              s6-linux-init/bin/s6-linux-init-shutdownd -c  "/etc/s6-linux-init/current" -g 3000
+            '';
+          mode = "0755";
+        };
+
+      };
+      s6-svscan-log = dir {
+        fifo = {
+          type = "i";
+          subtype = "f";
+          mode = "0600";
+        };
+        notification-fd = { file = "3"; };
+        run = {
+          file = ''
+              gdsgdfgsdgf
+          '';
+        };
+      };
+    };
+    uncaught-logs = (dir {}) // {mode = "2750";};
+  };
+in structure