chromium: add nixos module security.chromiumSuidSandbox

Closes #17460

Changed the wrapper derivation to produce a second output containing the sandbox.
Add a launch wrapper to try and locate the sandbox (either in /var/setuid-wrappers or in /nix/store).
This launch wrapper also sheds libredirect.so from LD_PRELOAD as Chromium does not tolerate it.

Does not trigger a Chromium rebuild.

cc @cleverca22 @joachifm @jasom

nixos/modules/security/chromium-suid-sandbox.nix

@@ -0,0 +1,28 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg     = config.security.chromiumSuidSandbox;
+  sandbox = pkgs.chromium.sandbox;
+in
+{
+  options.security.chromiumSuidSandbox.enable = mkEnableOption ''
+    Whether to install the Chromium SUID sandbox which is an executable that
+    Chromium may use in order to achieve sandboxing.
+
+    If you get the error "The SUID sandbox helper binary was found, but is not
+    configured correctly.", turning this on might help.
+
+    Also, if the URL chrome://sandbox tells you that "You are not adequately
+    sandboxed!", turning this on might resolve the issue.
+
+    Finally, if you have <option>security.grsecurity</option> enabled and you
+    use Chromium, you probably need this.
+  '';
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = [ sandbox ];
+    security.setuidPrograms    = [ sandbox.passthru.sandboxExecutableName ];
+  };
+}