Use Debian/ububtu patchset

dev-qt/qtwebkit/files/no_pdf_image_plugin.diff

@@ -0,0 +1,18 @@
+Description: do not attempt rendering PDF with Qt image plugin
+ Qt 5.15 added Qt PDF module which comes with imageformat plugin, which
+ allows rendering first page of PDF document as image.
+Origin: upstream, https://github.com/qtwebkit/qtwebkit/commit/0443d42b04e0f99c
+Last-Update: 2020-09-13
+
+--- a/Source/WebCore/platform/MIMETypeRegistry.cpp
++++ b/Source/WebCore/platform/MIMETypeRegistry.cpp
+@@ -254,6 +254,9 @@ static void initializeSupportedImageMIME
+     // Do not treat SVG as images directly because WebKit can handle them.
+     supportedImageMIMETypes->remove("image/svg+xml");
+     supportedImageResourceMIMETypes->remove("image/svg+xml");
++    // Do not treat PDF as images
++    supportedImageMIMETypes->remove("application/pdf");
++    supportedImageResourceMIMETypes->remove("application/pdf");
+ #endif // PLATFORM(QT)
+ #endif // USE(CG)
+ }