Add --print-deps-only for computing dependencies

llama_stack/cli/stack/build.py

@@ -63,6 +63,12 @@ environment is active, you must specify a name.
             ),
             default=None,
         )
+        self.parser.add_argument(
+            "--print-deps-only",
+            default=False,
+            action="store_true",
+            help="Print the dependencies for the stack only, without building the stack",
+        )
 
     def _run_stack_build_command(self, args: argparse.Namespace) -> None:
         # always keep implementation completely silo-ed away from CLI so CLI