some improvements for none cases

docs/source/distributions/building_distro.md

@@ -37,7 +37,7 @@ llama stack build
 
 > Enter a name for your Llama Stack (e.g. my-local-stack): my-stack
 > Enter the image type you want your Llama Stack to be built as (docker or conda): conda
-> Enter the target platform you want your Llama Stack to be built for: linux/arm64
+> Enter the target platform you want your Llama Stack to be built for:
 
 Llama Stack is composed of several APIs working together. Let's select
 the provider types (implementations) you want to use for these APIs.

llama_stack/cli/stack/build.py

@@ -80,6 +80,7 @@ class StackBuild(Subcommand):
         self.parser.add_argument(
             "--platform",
             type=str,
+            default=None,
             help="Platform to use for the build. Required when using docker as image type, defaults to host if no platform is specified",
         )
 
@@ -139,12 +140,7 @@ class StackBuild(Subcommand):
             )
 
             platform = prompt(
-                "> Enter the target platform you want your Llama Stack to be built for: ",
-                validator=Validator.from_callable(
-                    lambda x: len(x) > 0,
-                    error_message="Platform cannot be empty, please enter a platform",
-                ),
-                default="linux/arm64",
+                "> Enter the target platform you want your Llama Stack to be built for: "
             )
 
             cprint(
@@ -189,11 +185,10 @@ class StackBuild(Subcommand):
             )
 
             build_config = BuildConfig(
-                name=name,
-                image_type=image_type,
-                distribution_spec=distribution_spec,
-                platform=platform,
+                name=name, image_type=image_type, distribution_spec=distribution_spec
             )
+            if platform.strip():
+                build_config.platform = platform
             self._run_stack_build_command_from_build_config(build_config)
             return
 

llama_stack/distribution/build.py

@@ -121,6 +121,8 @@ def build_image(build_config: BuildConfig, build_file_path: Path):
             str(BUILDS_BASE_DIR / ImageType.docker.value),
             " ".join(normal_deps),
         ]
+        if build_config.platform is not None:
+            args.append(build_config.platform)
     elif build_config.image_type == ImageType.conda.value:
         script = pkg_resources.resource_filename(
             "llama_stack", "distribution/build_conda_env.sh"

llama_stack/distribution/datatypes.py

@@ -25,7 +25,6 @@ from llama_stack.providers.utils.kvstore.config import KVStoreConfig
 
 LLAMA_STACK_BUILD_CONFIG_VERSION = "2"
 LLAMA_STACK_RUN_CONFIG_VERSION = "2"
-LLAMA_STACK_DEFAULT_PLATFORM = "linux/arm64"
 
 
 RoutingKey = Union[str, List[str]]
@@ -168,7 +167,7 @@ class BuildConfig(BaseModel):
         default="conda",
         description="Type of package to build (conda | docker | venv)",
     )
-    platform: str = Field(
-        default=LLAMA_STACK_DEFAULT_PLATFORM,
-        description="The platform for docker image, defaults to linux/arm64",
+    platform: Optional[str] = Field(
+        default=None,
+        description="The platform for docker image",
     )