eglfs: obey QT_NO_REGULAREXPRESSION define

Not all platforms do have QRegularExpression as it is based on
pcre.

Change-Id: I6b8e701ff7cf30e776ee34e5dc836cd24c9543b5
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

src/plugins/platforms/eglfs/qeglfshooks_stub.cpp

@@ -63,11 +63,13 @@ QByteArray QEglFSHooks::fbDeviceName() const
 int QEglFSHooks::framebufferIndex() const
 {
     int fbIndex = 0;
+#ifndef QT_NO_REGULAREXPRESSION
     QRegularExpression fbIndexRx(QLatin1String("fb(\\d+)"));
     QRegularExpressionMatch match = fbIndexRx.match(fbDeviceName());
     if (match.hasMatch())
         fbIndex = match.captured(1).toInt();
 
+#endif
     return fbIndex;
 }