Updated "stackvm" target to have "cpu" key.

With the presence/absence of the "cpu" key in a target used to
determine whether host-only calls should be run, should make sure to
add it to "stackvm".

Author: Lunderberg

src/target/target_kind.cc

@@ -424,7 +424,8 @@ TVM_REGISTER_TARGET_KIND("hexagon", kDLHexagon)
     .add_attr_option<Integer>("vtcm-capacity")
     .set_default_keys({"hexagon"});
 
-TVM_REGISTER_TARGET_KIND("stackvm", kDLCPU);
+TVM_REGISTER_TARGET_KIND("stackvm", kDLCPU)  // line break
+    .set_default_keys({"cpu"});
 
 TVM_REGISTER_TARGET_KIND("ext_dev", kDLExtDev);