lg2: commit: add support for journal-only method

The design document for the new event system references an
option to log events to the journal rather than to dbus[1] using
the 'OPENBMC_MESSAGE_ID' identifier.  Add support and test cases
for this as a meson option.

[1]: https://github.com/openbmc/docs/blob/master/designs/event-logging.md#phosphor-logging

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I6cb94453c6cc95a9ccbbbc11859b70ef12d375fd
diff --git a/meson.options b/meson.options
index 0dd7c3e..2bab22c 100644
--- a/meson.options
+++ b/meson.options
@@ -41,3 +41,10 @@
     value: '/etc/rsyslog.d/server.conf',
     description: 'Path to rsyslog server conf file',
 )
+
+option(
+    'lg2_commit_strategy',
+    type: 'combo',
+    choices: ['dbus', 'journal', 'both'],
+    value: 'both'
+)