Implement initial version of fuzzing in CI (#7316)

* Implement initial version of fuzzing

* try nix config

* try rustup

* rustup run

* Fix syntax

* wip

* specific nightly

* wip

* specific nightly with+

* install

* locked

crates/compiler/test_syntax/fuzz/fuzz.nix

@@ -0,0 +1,25 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  buildInputs = [
+    (pkgs.rustup.override {
+      targets = ["x86_64-unknown-linux-gnu"]; # Adjust for your desired target
+    })
+  ];
+
+  shellHook = ''
+    # Ensure rustup is initialized
+    export RUSTUP_HOME="$PWD/.rustup"
+    export CARGO_HOME="$PWD/.cargo"
+    mkdir -p $RUSTUP_HOME $CARGO_HOME
+
+    # Install Rust nightly
+    rustup install nightly
+    rustup default nightly
+
+    # Add rustup and cargo to PATH
+    export PATH="$CARGO_HOME/bin:$PATH"
+
+    echo "Rust nightly and Cargo are available on PATH."
+  '';
+}