[libcalamares] Allow emergency jobs

Any job can be an emergency job; emergency modules spawn
emergency jobs (but conversely, a non-emergency module
can spawn an emergency job explicitly).

src/libcalamares/Job.h

@@ -66,8 +66,15 @@ public:
     virtual QString prettyDescription() const;
     virtual QString prettyStatusMessage() const;
     virtual JobResult exec() = 0;
+
+    bool isEmergency() const { return m_emergency; }
+    void setEmergency( bool e ) { m_emergency = e; }
+
 signals:
     void progress( qreal percent );
+
+private:
+    bool m_emergency = false;
 };
 
 } // namespace Calamares

src/libcalamaresui/ExecutionViewStep.cpp

@@ -21,6 +21,7 @@
 #include <ExecutionViewStep.h>
 
 #include "Branding.h"
+#include "Job.h"
 #include "JobQueue.h"
 #include "modulesystem/Module.h"
 #include "modulesystem/ModuleManager.h"
@@ -142,7 +143,15 @@ ExecutionViewStep::onActivate()
         Calamares::Module* module = Calamares::ModuleManager::instance()
                                     ->moduleInstance( instanceKey );
         if ( module )
-            queue->enqueue( module->jobs() );
+        {
+            auto jl = module->jobs();
+            if ( module->isEmergency() )
+            {
+                for( auto& j : jl )
+                    j->setEmergency( true );
+            }
+            queue->enqueue( jl );
+        }
     }
 
     queue->start();