title: QT5 error: Unknown type name 'QCoreApplication'. First program in Qt5
body: <p>I have just installed QTCreator in Linux Ubuntu 20.04 LTS, I clicked on File-&gt;New Project-&gt;Application-&gt;QTConsole Application. A first.pro file and main.cpp file was made.</p>
  <p>The first.pro contains:</p>
  <pre><code>QT -= gui declarative
  QT += widgets
  
  CONFIG += c++11 console
  CONFIG -= app_bundle
  
  DEFINES += QT_DEPRECATED_WARNINGS
  
  
  SOURCES += \
          main.cpp
  
  qnx: target.path = /tmp/$${TARGET}/bin
  else: unix:!android: target.path = /opt/$${TARGET}/bin
  !isEmpty(target.path): INSTALLS += target
  </code></pre>
  <p>The main.cpp contains:</p>
  <pre><code> #include &lt;QCoreApplication&gt;
  
  int main(int argc, char *argv[])
  {
      QCoreApplication a(argc, argv);
      return a.exec();
  }
  </code></pre>
  <p>The error comes in QCoreApplication line.</p>