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

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
-                   , hakyll >= 4.14
+  build-depends:     base == 4.*
+                   , hakyll == 4.15.*
                    , filepath >= 1.0
                    , pandoc >= 2.11
-                   , slugger >= 0.1.0.1
-                   , text >= 1.2 && < 1.3
-  ghc-options:       -Wall -threaded
-  default-language:  Haskell2010
+                   , slugger >= 0.1.0.2
+                   , text >= 1 && < 3
+  ghc-options:     -Wall
+                   -Wcompat
+                   -Widentities
+                   -Wincomplete-record-updates
+                   -Wincomplete-uni-patterns
+                   -Wpartial-fields
+                   -Wredundant-constraints
+                   -O2
+                   -threaded
+                   -rtsopts
+                   -with-rtsopts=-N