refac: workspace

flake.nix

@@ -72,9 +72,20 @@
           };
           strictDeps = true;
 
-          nativeBuildInputs = [
-            pkgs.pkg-config
-          ];
+          nativeBuildInputs =
+            [
+              pkgs.pkg-config
+            ]
+            ++ pkgs.lib.optionals pkgs.stdenv.hostPlatform.isLinux [
+              pkgs.mold
+            ];
+
+          # Link with mold (fast linker). Lives in commonArgs so deps and the
+          # final crate share one flag set; note this rebuilds all dependency
+          # crates once when first added.
+          env = pkgs.lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
+            RUSTFLAGS = "-C link-arg=-fuse-ld=mold";
+          };
 
           buildInputs =
             guiLibs
@@ -112,12 +123,16 @@
 
           # Put the GUI shared libraries on the runtime library path so winit
           # can dlopen libwayland and wgpu can find the vulkan loader.
-          shellHook = ''
-            export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:${pkgs.lib.makeLibraryPath guiLibs}"
-          '';
+          shellHook =
+            ''
+              export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:${pkgs.lib.makeLibraryPath guiLibs}"
+            ''
+            + pkgs.lib.optionalString pkgs.stdenv.hostPlatform.isLinux ''
+              export RUSTFLAGS="-C link-arg=-fuse-ld=mold"
+            '';
 
           # Extra inputs can be added here; cargo and rustc are provided by default.
-          packages = guiLibs;
+          packages = guiLibs ++ pkgs.lib.optionals pkgs.stdenv.hostPlatform.isLinux [ pkgs.mold ];
         };
       }
     );