flake: CI a *configure* test for static builds

Adding an entire second Lix build to test the static version is too
expensive for our current CI setup, but we can at least run the
up to the configure phase, which is a good premise.

Change-Id: I61e1ded7dd79698a9bb0f9a1d113b8b9963dfd44

flake.nix

@@ -140,10 +140,11 @@
               config.permittedInsecurePackages = [ "nix-2.13.6" ];
             };
           stdenvs = forAllStdenvs (make-pkgs null);
+          static-stdenvs = forAllStdenvs (name: (make-pkgs null name).pkgsStatic);
           native = stdenvs.stdenvPackages;
         in
         {
-          inherit stdenvs native;
+          inherit stdenvs native static-stdenvs;
           static = native.pkgsStatic;
           cross = forAllCrossSystems (crossSystem: make-pkgs crossSystem "stdenv");
         }
@@ -288,6 +289,22 @@
           );
         };
 
+        # Running a static build in CI for every CL is too expensive for us right now...
+        # But we can at least make sure it configures successfuly, which is cheap and where
+        # a good chunk of issues show up.
+        configure-static = forAvailableSystems (
+          system:
+          let
+            staticConfigure = self.packages.${system}.nix-static.overrideAttrs {
+              dontBuild = true;
+              installPhase = ''
+                mkdir -p "$out"
+              '';
+            };
+          in
+          lib.optionalAttrs (self.packages.${system} ? nix-static) staticConfigure
+        );
+
         pre-commit = forAvailableSystems (
           system:
           let
@@ -316,6 +333,9 @@
         // (lib.optionalAttrs (builtins.elem system linux64BitSystems)) {
           dockerImage = self.hydraJobs.dockerImage.${system};
         }
+        // (lib.optionalAttrs (self.hydraJobs.configure-static ? "${system}")) {
+          configure-static = self.hydraJobs.configure-static.${system};
+        }
       );
 
       packages = forAllSystems (