ProjectExplorer: Give build systems a name

... and make it accessible through a variable.

Fixes: QTCREATORBUG-26147
Change-Id: I0601c09a74360b91fe8421876207a8f4ae9d75b6
Reviewed-by: hjk <hjk@qt.io>

src/plugins/projectexplorer/project.cpp

@@ -1100,6 +1100,7 @@ public:
     using BuildSystem::BuildSystem;
 
     void triggerParsing() final {}
+    QString name() const final { return QLatin1String("test"); }
 };
 
 class TestProject : public Project