Add astyle test to Github Workflow

.github/actions/setup-nix/action.yml

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: Apache-2.0
+
+name: Setup nix
+description: Setup nix
+
+runs:
+  using: composite
+  steps:
+    - uses: nixbuild/nix-quick-install-action@v27
+      with: {load_nixConfig: false}
+    - name: Prepare nix dev shell
+      shell: nix develop .#ci -c bash -e {0}
+      run: |

.github/workflows/build.yml

@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: Apache-2.0
+
+name: Build
+on:
+  push:
+    branches: [ '*' ]
+  pull_request:
+    branches: [ "main" ]
+jobs:
+  build_test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Setup nix
+      uses: ./.github/actions/setup-nix
+    - name: Astyle
+      shell: nix develop .#ci -c bash -e {0}
+      run: |
+          err=$(astyle $(git ls-files "*.c" "*.h") --options=.astylerc --dry-run --formatted | awk '{print $2}')
+          if [[ ${#err} != 0 ]]; then
+            echo "$err" | while IFS= read -r file; do
+              echo "::error file={"$file"},title={checking}::Formatted $file"
+            done
+            exit 1
+          fi
+    - name: Build targets
+      shell: nix develop .#ci -c bash -e {0}
+      run: |
+          make

flake.nix

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+# SPDX-License-Identifier: Apache-2.0
+
+{
+  description = "mlkem-c-aarch64";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
+
+    flake-parts = {
+      url = "github:hercules-ci/flake-parts";
+      inputs.nixpkgs-lib.follows = "nixpkgs";
+    };
+  };
+
+  outputs = inputs@{ flake-parts, nixpkgs, ... }:
+    flake-parts.lib.mkFlake { inherit inputs; } {
+      imports = [ ];
+      systems = [ "x86_64-linux" "aarch64-linux" "aarch64-darwin" "x86_64-darwin" ];
+      perSystem = { pkgs, system, inputs', ... }:
+        let
+          core = with pkgs; [
+            # formatter & linters
+            astyle # 3.4.10
+          ];
+        in
+        {
+          devShells.default = with pkgs; mkShellNoCC {
+            packages = core ++ [
+              direnv
+              nix-direnv
+
+              # formatter & linters
+              nixpkgs-fmt
+              shfmt
+              codespell
+            ];
+
+            shellHook = ''
+              export PATH=$PWD/dev-support/bin:$PATH
+            '';
+          };
+
+          devShells.ci = with pkgs; mkShellNoCC {
+            packages = core;
+          };
+
+        };
+      flake = {
+        # The usual flake attributes can be defined here, including system-
+        # agnostic ones like nixosModule and system-enumerating ones, although
+        # those are more easily expressed in perSystem.
+
+      };
+    };
+}
+