AutoTest: Improve process error handling

If the test executable cannot be started or it seems
not to be the correct one or wrong arguments have been
passed to it the user now gets a respective message
inside the results pane.

Task-number: QTCREATORBUG-18955
Change-Id: Ica68cdbb9e401c8d48a9ce8b23b65d5410d2075a
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/plugins/autotest/testoutputreader.h

@@ -44,13 +44,17 @@ public:
 
     virtual void processOutput(const QByteArray &outputLine) = 0;
     virtual void processStdError(const QByteArray &output);
+    bool hadValidOutput() const { return m_hadValidOutput; }
 
 signals:
     void newOutputAvailable(const QByteArray &output);
 protected:
+    void reportResult(const TestResultPtr &result);
     QFutureInterface<TestResultPtr> m_futureInterface;
     QProcess *m_testApplication;  // not owned
     QString m_buildDir;
+private:
+    bool m_hadValidOutput = false;
 };
 
 } // namespace Internal