Add sdk dir for cmake to update

packages/zephyr/update.py

@@ -23,6 +23,8 @@ release = requests.get(
     "https://api.github.com/repos/zephyrproject-rtos/sdk-ng/releases/latest"
 ).json()
 tag = release["tag_name"]
+version = tag[1:]
+
 targets = []
 for asset in release["assets"]:
     if (
@@ -44,9 +46,15 @@ for target in targets:
         url = f"https://github.com/zephyrproject-rtos/sdk-ng/releases/download/v0.16.3/toolchain_linux-{host}_{target}.tar.xz"
         toolchains[target][host + "-linux"] = {"url": url, "hash": prefetch_file(url)}
 
+# Yes, macOS. We just want the cmake sources, which are identical,
+# but don't need another copy of the host tools, which are only in linux
+sdk_url = f"https://github.com/zephyrproject-rtos/sdk-ng/releases/download/{tag}/zephyr-sdk-{version}_macos-aarch64_minimal.tar.xz"
+sdk = {"url": sdk_url, "hash": prefetch_file(sdk_url)}
+
 out_obj = {
-    "version": tag[1:],
+    "version": version,
     "hosts": list(map(lambda arch: arch + "-linux", HOSTS)),
+    "sdk": sdk,
     "host_tools": host_tools,
     "toolchains": toolchains,
 }