AutoTest: Extract code into function

Part of a later refactoring.

Change-Id: I8321b344ff333195905be68131aab508d1a87aee
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/autotest/testrunner.h

@@ -71,6 +71,8 @@ private:
     void buildFinished(bool success);
     void onFinished();
 
+    int precheckTestConfigurations();
+
     void runTests();
     void debugTests();
     void runOrDebugTests();