nix: added nightly to config flags

Use
```
nix-build --arg config '{ nightly = true; }' -A nightly-checks.ouroboros-network-framework
```
to build nightly checks of `ouroboros-network-framework`.

default.nix

@@ -8,7 +8,9 @@
   # }'
 , sourcesOverride ? { }
   # pinned version of nixpkgs augmented with overlays (iohk-nix and our packages).
-, pkgs ? import ./nix { inherit system crossSystem config sourcesOverride; }
+  , pkgs ? import ./nix { inherit system crossSystem sourcesOverride;
+                          config = { nightly = false; } // config;
+                        }
 , gitrev ? pkgs.iohkNix.commitIdFromGitRepoOrZero ./.git }:
 with pkgs;
 with commonLib;
@@ -61,6 +63,10 @@ let
         haskellPackages.ouroboros-consensus-cardano-test.components.tests.test;
       Shelley =
         haskellPackages.ouroboros-consensus-shelley-test.components.tests.test;
+      ouroboros-network-framework =
+        haskellPackages.ouroboros-network-framework.components.tests.test;
+      ouroboros-network =
+        haskellPackages.ouroboros-network.components.tests.test;
     };
 
     shell = import ./shell.nix {

nix/ouroboros-network.nix

@@ -4,7 +4,8 @@
 { lib, stdenv, pkgs, haskell-nix, buildPackages, config ? { }
   # Enable profiling
 , profiling ? config.haskellNix.profiling or false
-, libsodium-vrf ? pkgs.libsodium-vrf }:
+, libsodium-vrf ? pkgs.libsodium-vrf
+}:
 let
   compiler-nix-name = pkgs.localConfig.ghcVersion;
   src = haskell-nix.haskellLib.cleanGit {
@@ -78,6 +79,7 @@ let
             "xhtml"
             # "stm" "terminfo"
           ];
+          packages.ouroboros-network-testing.flags.nightly = config.nightly;
           # ruby/perl dependencies cannot be cross-built for cddl tests:
           packages.ouroboros-network.flags.cddl = false;
 
@@ -110,6 +112,7 @@ let
       # Options for when not compiling to windows:
       ({ pkgs, ... }:
         lib.mkIf (!pkgs.stdenv.hostPlatform.isWindows) {
+          packages.ouroboros-network-testing.flags.nightly = config.nightly;
           packages.ouroboros-network.flags.cddl = true;
           packages.ouroboros-network.components.tests.cddl.build-tools =
             [ pkgs.cddl pkgs.cbor-diag ];