RunConfiguration: Introduce buildSystemTarget()

Introduce a method that maps a RunConfiguration to the build system target
that created the executable.

Implement the method in all RunConfigurations where that makes sense (e.g.
no CustomExecutables).

Change-Id: Ifaac859c2cd9b2806a0d7c185b2239312a67752a
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/qmakeprojectmanager/qmakeproject.cpp

@@ -1546,6 +1546,13 @@ QmakeProject::AsyncUpdateState QmakeProject::asyncUpdateState() const
     return m_asyncUpdateState;
 }
 
+QString QmakeProject::mapProFilePathToTarget(const FileName &proFilePath)
+{
+    const QmakeProjectManager::QmakeProFileNode *root = rootProjectNode();
+    const QmakeProjectManager::QmakeProFileNode *node = root ? root->findProFileFor(proFilePath) : nullptr;
+    return node ? node->targetInformation().target : QString();
+}
+
 } // namespace QmakeProjectManager
 
 #include "qmakeproject.moc"