flake: add rust devshell

flake.nix

@@ -82,6 +82,11 @@
           ];
           RUST_SRC_PATH = "${rust}/lib/rustlib/src/rust/library";
         };
+        devShells.rust = with pkgs;
+          mkShell {
+            nativeBuildInputs = [ rustc cargo rustfmt clippy ];
+            RUST_SRC_PATH = "${rust.packages.stable.rustPlatform.rustLibSrc}";
+          };
         devShells.avr = with pkgs;
           pkgsCross.avr.mkShell {
             packages = [ avrdude gnumake ];

rust/.envrc

@@ -0,0 +1 @@
+use flake ..#rust