Update acloud default target to 64 bit.

The default target name would like cf_x86_64_phone-userdebug.

Bug: 173736646
Test: acloud-dev create
Change-Id: I0051476a0885e834472a1d24d9e0432de0345f10
diff --git a/create/avd_spec.py b/create/avd_spec.py
index b466f20..d0eb849 100644
--- a/create/avd_spec.py
+++ b/create/avd_spec.py
@@ -45,7 +45,7 @@
 _COMMAND_REPO_INFO = "repo info platform/tools/acloud"
 _REPO_TIMEOUT = 3
 _CF_ZIP_PATTERN = "*img*.zip"
-_DEFAULT_BUILD_BITNESS = "x86"
+_DEFAULT_BUILD_BITNESS = "x86_64"
 _DEFAULT_BUILD_TYPE = "userdebug"
 _ENV_ANDROID_PRODUCT_OUT = "ANDROID_PRODUCT_OUT"
 _ENV_ANDROID_BUILD_TOP = "ANDROID_BUILD_TOP"
@@ -669,7 +669,7 @@
 
         Target = {REPO_PREFIX}{avd_type}_{bitness}_{flavor}-
             {DEFAULT_BUILD_TARGET_TYPE}.
-        Example target: aosp_cf_x86_phone-userdebug
+        Example target: aosp_cf_x86_64_phone-userdebug
 
         Args:
             args: Namespace object from argparse.parse_args.
diff --git a/create/avd_spec_test.py b/create/avd_spec_test.py
index 82de209..511e2a9 100644
--- a/create/avd_spec_test.py
+++ b/create/avd_spec_test.py
@@ -188,21 +188,21 @@
         self.args.avd_type = constants.TYPE_GCE
         self.assertEqual(
             self.AvdSpec._GetBuildTarget(self.args),
-            "gce_x86_iot-userdebug")
+            "gce_x86_64_iot-userdebug")
 
         self.AvdSpec._remote_image[constants.BUILD_BRANCH] = "aosp-master"
         self.AvdSpec._flavor = constants.FLAVOR_PHONE
         self.args.avd_type = constants.TYPE_CF
         self.assertEqual(
             self.AvdSpec._GetBuildTarget(self.args),
-            "aosp_cf_x86_phone-userdebug")
+            "aosp_cf_x86_64_phone-userdebug")
 
         self.AvdSpec._remote_image[constants.BUILD_BRANCH] = "git_branch"
         self.AvdSpec._flavor = constants.FLAVOR_PHONE
         self.args.avd_type = constants.TYPE_CF
         self.assertEqual(
             self.AvdSpec._GetBuildTarget(self.args),
-            "cf_x86_phone-userdebug")
+            "cf_x86_64_phone-userdebug")
 
     # pylint: disable=protected-access
     def testProcessHWPropertyWithInvalidArgs(self):