[AutoTVM] Use new target object

Use new target object tvm.target.Targe(), which now holds both 'target'
and 'target_host', in AutoTVM measurement functions. At some point the
tvm.driver.build() will be called by AutoTVM and it expects now such a
kind of target instead of the old (separate) one for 'target' and
'target_host'.

This avoids several deprecate warning messages caused by build() when
AutoTVM is used by tools like 'tvmc'.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>

python/tvm/autotvm/measure/measure_methods.py

@@ -44,6 +44,7 @@
 from tvm.contrib.popen_pool import PopenPoolExecutor
 from tvm.driver import build
 from tvm.error import TVMError
+from tvm.ir.container import Map
 from tvm.target import Target
 
 from ..env import AutotvmGlobalScope
@@ -496,7 +497,8 @@ def set_task(self, task):
 def _build_func_common(measure_input, runtime=None, check_gpu=None, build_option=None):
     """Common part for building a configuration"""
     target, task, config = measure_input
-    target, task.target_host = Target.check_and_update_host_consist(target, task.target_host)
+    assert not isinstance(target, (Map, dict)), "It's expected that 'target' is a string here."
+    target, _ = Target.check_and_update_host_consist(target, task.target_host)
 
     with target:
         s, args = task.instantiate(config)
@@ -520,7 +522,7 @@ def _build_func_common(measure_input, runtime=None, check_gpu=None, build_option
             func = vta.build(s, args, target_host=task.target_host)
         else:
             with tvm.ir.transform.PassContext(config=opts):
-                func = build(s, args, target_host=task.target_host, runtime=runtime)
+                func = build(s, args, target=target, runtime=runtime)
     return func, tuple((get_const_tuple(x.shape), x.dtype) for x in args)