Fix qt6 autopkgtest

debian/tests/qt6

@@ -10,5 +10,5 @@ else
 fi
 
 cd $AUTOPKGTEST_TMP
-${CROSS_COMPILE}g++ -Wall -Werror -pedantic -Wno-long-long -Wno-deprecated-declarations -fPIC -std=c++11 -o poppler-qt6-test $SRCDIR/test-qt6.cpp `${CROSS_COMPILE}pkg-config --cflags --libs poppler-qt6 qt6Core`
+${CROSS_COMPILE}g++ -Wall -Werror -pedantic -Wno-long-long -Wno-deprecated-declarations -fPIC -std=c++17 -o poppler-qt6-test $SRCDIR/test-qt6.cpp `${CROSS_COMPILE}pkg-config --cflags --libs poppler-qt6 Qt6Core`
 ./poppler-qt6-test "/usr/share/cups/data/default-testpage.pdf"

debian/tests/test-qt6.cpp

+#include <poppler-qt6.h>
+#include <QtCore/QFile>
+#include <stdlib.h>
+
+int main(int argc, char *argv[])
+{
+  if (argc < 2)
+    return EXIT_FAILURE;
+
+  std::unique_ptr<Poppler::Document> doc = Poppler::Document::load(QFile::decodeName(argv[1]));
+  Q_ASSERT(doc);
+  Q_ASSERT(!doc->isLocked());
+
+  int n_pages = doc->numPages();
+  Q_ASSERT(n_pages > 0);
+
+  return EXIT_SUCCESS;
+}