system/ccache: init and add to hyacinth

modules/system/ccache.nix

@@ -0,0 +1,30 @@
+{ config, ... }: {
+  programs.ccache.enable = true;
+  nixpkgs.overlays = [
+    (self: super: {
+      ccacheWrapper = super.ccacheWrapper.override {
+        extraConfig = ''
+          export CCACHE_COMPRESS=1
+          export CCACHE_DIR="${config.programs.ccache.cacheDir}"
+          export CCACHE_UMASK=007
+          if [ ! -d "$CCACHE_DIR" ]; then
+            echo "====="
+            echo "Directory '$CCACHE_DIR' does not exist"
+            echo "Please create it with:"
+            echo "  sudo mkdir -m0770 '$CCACHE_DIR'"
+            echo "  sudo chown root:nixbld '$CCACHE_DIR'"
+            echo "====="
+            exit 1
+          fi
+          if [ ! -w "$CCACHE_DIR" ]; then
+            echo "====="
+            echo "Directory '$CCACHE_DIR' is not accessible for user $(whoami)"
+            echo "Please verify its access permissions"
+            echo "====="
+            exit 1
+          fi
+        '';
+      };
+    })
+  ];
+}

modules/system/nix.nix

@@ -3,6 +3,7 @@
     package = pkgs.nixUnstable;
 
     settings = rec {
+      extra-sandbox-paths = [ config.programs.ccache.cacheDir ];
       substituters = [
         "https://cache.nixos.org?priority=10"
         "https://lava.cachix.org"