Flatpak: Work around patched libpng in org.freedesktop.Sdk

see
<https://github.com/flathub/org.libreoffice.LibreOffice/pull/268/commits/7c79189f674c7cc88f0ab2790d8d198f4a855182>
"Work around patched libpng in org.freedesktop.Sdk":

...which carries
<https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/commit/873b28450476c434a3f6fa86cb1874b11968a479>
"elements/base/libpng.bst: Add support for animated PNGs", thus handles "acTL"
chunks by itself, thus doesn't call the LibreOffice handle_unknown_chunk
function (in vcl/source/filter/png/PngImageReader.cxx) for such chunks, thus
never sets APNGInfo::mbIsApng to true, so causes CppunitTest_vcl_png_test to
fail with

> PngFilterTest.cxx:382:Assertion
> Test name: PngFilterTest::testApng
> assertion failed
> - Expression: aGraphic.IsAnimated()

(<https://buildbot.flathub.org/#/builders/6/builds/92958>) since
<https://git.libreoffice.org/core/+/bf944e33569e4a1d6236a54671b7320cdc6ffaf6%5E%21>
"tdf#104877 Add basic APNG format support".

The patch appears to originate from
<https://sourceforge.net/projects/libpng-apng/>, and it might be possible to
adapt the LibreOffice code to also work with such a patched libpng (whose png.h
defines PNG_APGN_SUPPORTED).  However, for now just use LibreOffice's own
external/libpng instead of the patched one.

Change-Id: Ib67056d11dfa6456920a18216a3b2bbec45f3662
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/162112
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>
(cherry picked from commit 223bfa24cdeee2ed45ff8d9ab7bb0b92eb8af587)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/162107
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>

0 files changed, 0 insertions, 0 deletions