nix: comment out libkrun(fw) source overrides

As we're currently using entirely upstream ones right now. Let's reuse
the cache.nixos.org builds.

packages/libkrun/default.nix

@@ -1,18 +1,30 @@
-{ libkrun, libkrunfw, libkrun-src, rustPlatform, variant ? null, ... }:
+{
+  libkrun,
+  libkrunfw,
+  # libkrun-src,
+  # rustPlatform,
+  variant ? null,
+  ...
+}:
 
 let
   libkrunfw' = libkrunfw.override { inherit variant; };
-in
-(libkrun.override {
-  withBlk = true;
-  withGpu = true;
-  withSound = true;
-  withNet = true;
-  inherit variant;
-  libkrunfw = libkrunfw';
-}).overrideAttrs (old: {
-  src = libkrun-src;
-  cargoDeps = rustPlatform.importCargoLock {
-    lockFile = "${libkrun-src}/Cargo.lock";
+  libkrun' = libkrun.override {
+    withBlk = true;
+    withNet = true;
+    withGpu = true;
+    # --- stick to the override used in nixpkgs' muvm package to reuse nixos.org cache when not overriding src ---
+    # withSound = true; # not for pipewire forwarding, anyway
+    # withTimesync = true; # why not?..
+    # ---------
+    inherit variant;
+    libkrunfw = libkrunfw';
   };
-})
+in
+libkrun'
+# libkrun'.overrideAttrs (old: {
+#   src = libkrun-src;
+#   cargoDeps = rustPlatform.importCargoLock {
+#     lockFile = "${libkrun-src}/Cargo.lock";
+#   };
+# })