native modules: build rust workspace crates through the repo flake

dimos/core/native_module.py

@@ -47,6 +47,7 @@ class MyCppModule(NativeModule):
 import json
 import os
 from pathlib import Path
+import shutil
 import signal
 import subprocess
 import sys
@@ -480,11 +481,17 @@ def _maybe_build(self) -> None:
             build_command=self.config.build_command,
         )
         build_start = time.perf_counter()
+        env = {**os.environ, **self.config.extra_env}
+        # Non-interactive shells (ssh commands, systemd) miss the rustup PATH entry, so
+        # cargo build commands die with exit 127 there.
+        cargo_dir = Path.home() / ".cargo" / "bin"
+        if shutil.which("cargo") is None and (cargo_dir / "cargo").exists():
+            env["PATH"] = f"{cargo_dir}{os.pathsep}{env.get('PATH', '')}"
         proc = subprocess.Popen(
             self.config.build_command,
             shell=True,
             cwd=self.config.cwd,
-            env={**os.environ, **self.config.extra_env},
+            env=env,
             stdout=subprocess.PIPE,
             stderr=subprocess.STDOUT,
         )