build: Add delayed_replay_queue option

When folder session is claimed, that can lock for some ms.
It can be tricky to debug issues happening during this small random delay.
Use this build option to force the delay.

meson_options.txt

@@ -70,3 +70,9 @@ option(
   value: 'enabled',
   description: 'Support Microsoft-proprietary TNEF attachments.'
 )
+option(
+  'delayed_replay_queue',
+  type: 'boolean',
+  value: false,
+  description: 'Add delay in session opening (for debug purpose only)'
+)

src/engine/imap-engine/imap-engine-minimal-folder.vala

@@ -1030,6 +1030,12 @@ private class Geary.ImapEngine.MinimalFolder : Geary.Folder, Geary.FolderSupport
 
         Imap.FolderSession? session = null;
         try {
+#if WITH_DELAYED_REPLAY_QUEUE
+            // When folder session is claimed, that can lock for some ms.
+            // It can be tricky to debug issues happening during this small
+            // random delay. Use this build option to force the delay.
+            yield Geary.Scheduler.sleep_async(1);
+#endif
             session = yield this._account.claim_folder_session(
                 this.path, cancellable
             );

src/engine/meson.build

@@ -365,6 +365,12 @@ if libytnef.found()
   ]
 endif
 
+if get_option('delayed_replay_queue')
+  engine_vala_args += [
+    '-D', 'WITH_DELAYED_REPLAY_QUEUE'
+  ]
+endif
+
 engine_lib = static_library('geary-engine',
   engine_sources,
   dependencies: engine_dependencies,