[Target] Print deprecation warning before canonicalisation in build m…

…odule (#12747)

Hopefully fixes #12742, as the warning should only be printed when a user passes `target_host`, in the current case if the user passes `None` as `target_host` it'll be processed by `canon_target_map_and_host` which seems to always produce a `target_host` and thus triggering the warning despite the user doing nothing wrong.

python/tvm/driver/build_module.py

@@ -258,15 +258,15 @@ def build(
             raise ValueError("inputs must be Schedule, IRModule," "or dict of str to IRModule.")
         annotated_mods[tar] = mod.with_attr("runtime", runtime)
 
-    annotated_mods, target_host = Target.canon_target_map_and_host(annotated_mods, target_host)
-
     # TODO(mbs): Both CompilationConfig and TIRToRuntime implement the same host target
     #  defaulting logic, but there's currently no way to get back the decided host.
     if target_host is not None:
         warnings.warn(
             "target_host parameter is going to be deprecated. "
             "Please pass in tvm.target.Target(target, host=target_host) instead."
         )
+
+    annotated_mods, target_host = Target.canon_target_map_and_host(annotated_mods, target_host)
     if not target_host:
         for tar, mod in annotated_mods.items():
             device_type = ndarray.device(tar.kind.name, 0).device_type