ProjectExplorer: Allow to schedule a build/run during a project parse

Once we parsed the project initially, subsequent parses typically do not
change things in a major way, so we can expect e.g. run configurations to
stay intact.
It therefore makes sense to allow users to schedule an
application run not only during a build (see 4b92b7ac60), but also
during a parse. Arguably, this is even more relevant, as parsing is
usually not triggered directly by the user, but happens as a side effect
of editing a document or switching a branch. It is then annoying for
users to have to wait until the respective buttons get enabled again.

Fixes: QTCREATORBUG-24986
Change-Id: I1081ccde668eee794c39b96cd0bad5c3aaa580bc
Reviewed-by: hjk <hjk@qt.io>

src/plugins/qbsprojectmanager/qbsbuildstep.cpp

@@ -199,7 +199,7 @@ QbsBuildStep::~QbsBuildStep()
 
 bool QbsBuildStep::init()
 {
-    if (qbsBuildSystem()->isParsing() || m_session)
+    if (m_session)
         return false;
 
     auto bc = static_cast<QbsBuildConfiguration *>(buildConfiguration());