add #fuzz devshell and make fuzzing work on nixos

Cargo.lock

@@ -1548,6 +1548,7 @@ name = "garage-fuzz"
 version = "0.0.0"
 dependencies = [
  "arbitrary",
+ "garage_db",
  "garage_model",
  "garage_table",
  "libfuzzer-sys",

flake.nix

@@ -95,6 +95,14 @@
                 killall
               ];
             };
+
+            # dev shell for fuzzing
+            fuzz = pkgs.mkShell {
+              buildInputs = with pkgs; [
+                targets.toolchainNightly
+                cargo-fuzz
+              ];
+            };
           };
       });
 }

fuzz/Cargo.toml

@@ -11,12 +11,9 @@ cargo-fuzz = true
 arbitrary = { workspace = true, features = ["derive"]}
 libfuzzer-sys = { workspace = true }
 
-[dependencies.garage_table]
-path = "../src/table"
-
-[dependencies.garage_model]
-path = "../src/model"
-features = ["arbitrary"]
+garage_db.workspace = true
+garage_table.workspace = true
+garage_model = { workspace = true, default-features = false, features = ["arbitrary"] }
 
 [[bin]]
 name = "version_crdt"

nix/compile.nix

@@ -148,6 +148,14 @@ let
 in rec {
   toolchain = toolchainFn pkgs;
 
+  toolchainNightly = pkgs.rust-bin.selectLatestNightlyWith (toolchain: toolchain.default.override {
+    targets = lib.optionals (target != null) [ rustTarget ];
+    extensions = [
+      "rust-src"
+      "rustfmt"
+    ];
+  });
+
   devShell = pkgs.mkShell {
     buildInputs = [
       toolchain