Fixed build error on macos (#33200)

This was due to uname reporting the architecture as arm64
instead of aarch64 on macos

Signed-off-by: Benjamin Vincent Schulenburg <bennyschulenburg@gmx.de>

python/servo/platform/__init__.py

@@ -40,7 +40,7 @@ def host_triple():
         cpu_type = "x86_64"
     elif cpu_type == "arm":
         cpu_type = "arm"
-    elif cpu_type == "aarch64":
+    elif cpu_type in ["aarch64", "arm64"]:
         cpu_type = "aarch64"
     else:
         cpu_type = "unknown"