[partition] Insert annoying 3-sec delay

This is intended for testing -- it helps debug where a slow
requirement check blocks the UI.

src/modules/partition/gui/PartitionViewStep.cpp

@@ -56,6 +56,8 @@
 #include <QtConcurrent/QtConcurrent>
 #include <QFutureWatcher>
 
+#include <unistd.h>  // For sleep(3)
+
 PartitionViewStep::PartitionViewStep( QObject* parent )
     : Calamares::ViewStep( parent )
     , m_core( nullptr )
@@ -565,6 +567,8 @@ Calamares::RequirementsList PartitionViewStep::checkRequirements()
     if (m_future)
         m_future->waitForFinished();
 
+    sleep(3);
+
     Calamares::RequirementsList l;
     l.append(
     {