Add patch to enforce offline mode in forc-node build script for dependency on fuel-core.

Author: JoshuaBatty

patches.nix

@@ -154,6 +154,21 @@ in [
     };
   }
 
+  {
+    condition = m: m.pname == "forc-node";
+    patch = m: {
+      # `fuel-core` vendors a build script that shells out to `cargo install`
+      # for the WASM executor. During a Nix build we have no network, so we
+      # rewrite the script to force cargo offline mode.
+      postPatch = (m.postPatch or "") + ''
+        find . -path '*/fuel-core-*/crates/services/upgradable-executor/build.rs' -print0 | while IFS= read -r -d '\0' f; do
+          perl -0pi -e 's/let mut args = vec!\[\n/let mut args = vec![\n        "--offline".to_owned(),\n/' "$f"
+          perl -0pi -e 's/cargo.env\("CARGO_PROFILE_RELEASE_DEBUG", "false"\);\n/cargo.env("CARGO_PROFILE_RELEASE_DEBUG", "false");\n    cargo.env("CARGO_NET_OFFLINE", "true");\n/' "$f"
+        done
+      '';
+    };
+  }
+
   # The forc plugins that reside in the Sway repo are in a dedicated
   # subdirectory.
   {