nginx: add PageSpeed module (Linux only)

pkgs/servers/http/nginx/modules.nix

@@ -146,4 +146,33 @@
       sha256 = "0ib2jrbjwrhvmihhnzkp4w87fxssbbmmmj6lfdwpm6ni8p9g60dw";
     };
   };
+
+  pagespeed =
+    let
+      version = pkgs.psol.version;
+
+      moduleSrc = fetchFromGitHub {
+        owner  = "pagespeed";
+        repo   = "ngx_pagespeed";
+        rev    = "v${version}-beta";
+        sha256 = "03dvzf1lgsjxcs1jjxq95n2rhgq0wy0f9ahvgascy0fak7qx4xj9";
+      };
+
+      ngx_pagespeed = pkgs.runCommand
+        "ngx_pagespeed"
+        {
+          meta = {
+            description = "PageSpeed module for Nginx";
+            homepage    = "https://developers.google.com/speed/pagespeed/module/";
+            license     = pkgs.stdenv.lib.licenses.asl20;
+          };
+        }
+        ''
+          cp -r "${moduleSrc}" "$out"
+          chmod -R +w "$out"
+          ln -s "${pkgs.psol}" "$out/psol"
+        '';
+    in {
+      src = ngx_pagespeed;
+    };
 }