fix build by updating cabal file and getting some nix things in line

flake.nix

@@ -24,6 +24,7 @@
             hakyllProject = final.haskell-nix.project' {
               src = ./ssg;
               compiler-nix-name = "ghc948";
+              modules = [{ doHaddock = false; }];
               shell.buildInputs = [
                 hakyll-site
               ];
@@ -43,7 +44,9 @@
 
         flake = pkgs.hakyllProject.flake {};
 
-        hakyll-site = flake.packages."ssg:exe:hakyll-site";
+        executable = "ssg:exe:hakyll-site";
+
+        hakyll-site = flake.packages.${executable};
 
         website = pkgs.stdenv.mkDerivation {
           name = "website";
@@ -64,7 +67,7 @@
             "${pkgs.glibcLocales}/lib/locale/locale-archive";
 
           buildPhase = ''
-            ${hakyll-site}/bin/hakyll-site build --verbose
+            ${flake.packages.${executable}}/bin/hakyll-site build --verbose
           '';
 
           installPhase = ''

ssg/ssg.cabal

@@ -1,4 +1,4 @@
-cabal-version:       2.4
+cabal-version:       3.6
 
 name:                ssg
 version:             0.1.0.0
@@ -7,13 +7,23 @@ license:             BSD-3-Clause
 license-file:        LICENSE
 
 executable hakyll-site
+  default-language:  Haskell2010
   main-is:           Main.hs
   hs-source-dirs:    src
-  build-depends:     base >= 4.8
+  build-depends:     base == 4.*
-                   , hakyll >= 4.14
+                   , hakyll == 4.15.*
                    , filepath >= 1.0
                    , pandoc >= 2.11
-                   , slugger >= 0.1.0.1
+                   , slugger >= 0.1.0.2
-                   , text >= 1.2 && < 1.3
+                   , text >= 1 && < 3
-  ghc-options:       -Wall -threaded
+  ghc-options:     -Wall
-  default-language:  Haskell2010
+                   -Wcompat
+                   -Widentities
+                   -Wincomplete-record-updates
+                   -Wincomplete-uni-patterns
+                   -Wpartial-fields
+                   -Wredundant-constraints
+                   -O2
+                   -threaded
+                   -rtsopts
+                   -with-rtsopts=-N