AbstractProcessStep: Do not run a qprocess in a thread

This avoids sending signals for new tasks and process output
via the gui thread's event loop. When finding lots of issues in
the output we generate so many events that any attempt to
compress events takes a long time (max. events waiting to be
processed were > 1200000 when doing a clang -Weverything build!),
and thus the UI freezes.

Change-Id: I9668d2537b1a268e788cd0ea5c756ebaab4462a9
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/plugins/cmakeprojectmanager/makestep.cpp

@@ -219,6 +219,7 @@ void MakeStep::run(QFutureInterface<bool> &fi)
     if (!canContinue) {
         emit addOutput(tr("Configuration is faulty. Check the Issues view for details."), BuildStep::MessageOutput);
         fi.reportResult(false);
+        emit finished();
         return;
     }