Add default time sync object path

The time sync object path is empty by default and is initialized by a
dbus call at runtime.
It works OK in BMC but the unit tests in the repo is broken due to the
empty string used in the sdbus matcht_t.

Add a config option to initialize the default time sync object path, so
that it works both on BMC and in unit tests.

Signed-off-by: Lei YU <yulei.sh@bytedance.com>
Change-Id: Iccdaef58434a1227c4ea73230ba23b4e618a2d2d
diff --git a/meson_options.txt b/meson_options.txt
index 92d1f11..d4b7fa6 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -17,3 +17,10 @@
           choices: ['Mode::Manual', 'Mode::NTP'],
           value : 'Mode::Manual',
           description : 'The default time mode')
+
+option(
+    'default_time_sync_object_path',
+    type: 'string',
+    value: '/xyz/openbmc_project/time/sync_method',
+    description: 'Default object path for time sync setting'
+)