nix: hack static-haskell-nix for updated nixpkgs

This patches static-haskell-nix to work for building postgrest
with updated nixpkgs (from ~202203):

- The ncurses 'enableStatic' argument doesn't exist anymore.
  We use the vanilla package instead, which seems to work fine.
- The 'isExecutable' check fails with a strange error related
  to trying to override 'mkDerivation'.
  We patch 'isExecutable' to check explicitly whether we're building
  postgrest. ('isExecutable' is used to determine whether to build
  a package statically.)

nix/patches/default.nix

@@ -21,4 +21,9 @@
   # See: https://github.com/NixOS/nixpkgs/pull/87879
   nixpkgs-openssl-split-runtime-dependencies-of-static-builds =
     ./nixpkgs-openssl-split-runtime-dependencies-of-static-builds.patch;
+
+  static-haskell-nix-ncurses =
+    ./static-haskell-nix-ncurses.patch;
+  static-haskell-nix-isexecutable =
+    ./static-haskell-nix-isexecutable.patch;
 }