Code polishing, continuing cb23999fbf

Add more error messages to processes run for toolchain detection.
Move Windows-specific code to dbgwinutils, remove inclusion of
<windows.h>. Fix MinGW gcc 4.5 warnings.

src/plugins/qt4projectmanager/qtversionmanager.cpp

@@ -1096,6 +1096,10 @@ static bool queryQMakeVariables(const QString &binary, QHash<QString, QString> *
         qWarning("Timeout running '%s' (%dms).", qPrintable(binary), timeOutMS);
         return false;
     }
+    if (process.exitStatus() != QProcess::NormalExit) {
+        qWarning("'%s' crashed.", qPrintable(binary));
+        return false;
+    }
     QByteArray output = process.readAllStandardOutput();
     QTextStream stream(&output);
     while (!stream.atEnd()) {