Fix cargo2rulesmk.py dependency bug in sandbox

Remove the check performed by cargo2rulesmk.py
whether the external/rust/crates/{name} directories
exist for all dependencies of the current crate.
These directories only exist in the Android tree,
not in the minimal checkout inside the redshell sandbox.

Bug: 281857510
Test: cargo2rulesmk.py on thiserror-impl
Change-Id: I1e5d46b4de3129770ab87ebc5e58563010ae6605

scripts/cargo2rulesmk.py

@@ -596,25 +596,14 @@ class Crate(object):
             path = CUSTOM_MODULE_CRATES.get(
                 name, f"external/rust/crates/{name}"
             )
-            abspath = os.path.normpath(os.path.join(TOP_DIR, path))
+            if dependency["optional"]:
-            # just check for directory, not whether it contains rules.mk, since
-            # we do not generate makefile rules in topological order
-            if os.path.isdir(abspath):
-                library_deps.append(path)
-            elif dependency["optional"]:
                 if feats := [
                     f
                     for f in self.features
                     if name in self.feature_dependencies.get(f, [])
                 ]:
-                    print(
+                    continue
-                        f"### WARNING: missing dependency {name} needed by features "
+            library_deps.append(path)
-                        + ", ".join(feats)
-                    )
-                    return
-            else:
-                print(f"### WARNING: missing non-optional dependency: {path}")
-                return
         if library_deps:
             self.write("MODULE_LIBRARY_DEPS := \\")
             for path in library_deps: