Bump libpng to 1.6.55

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e354260..1fdcd9d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,7 +46,7 @@
 * Update rav1e.cmd/LocalRav1e.cmake: cargo-c v0.10.20, corrosion v0.6.1,
   rav1e v0.8.1
 * Update svt.cmd/svt.sh/LocalSvt.cmake: v4.0.1
-* Update zlibpng.cmd/LocalZlibpng.cmake: libpng 1.6.51, zlib 1.3.2
+* Update zlibpng.cmd/LocalZlibpng.cmake: libpng 1.6.55, zlib 1.3.2
 * Fix grayscale conversion when changing the bit depth.
 * Bump cmake_minimum_required from 3.13 to 3.22
 * Associate transformative properties with alpha auxiliary image items.

cmake/Modules/LocalZlibpng.cmake

diff --git a/cmake/Modules/LocalZlibpng.cmake b/cmake/Modules/LocalZlibpng.cmake
index 5ecf679..a87bdab 100644
--- a/cmake/Modules/LocalZlibpng.cmake
+++ b/cmake/Modules/LocalZlibpng.cmake
@@ -1,6 +1,5 @@
 set(AVIF_ZLIB_GIT_TAG v1.3.2)
-# v1.6.51 and v1.6.53 confuse CMake by giving Unix flags with MSVC on ci-windows.yml
-set(AVIF_LIBPNG_GIT_TAG v1.6.51)
+set(AVIF_LIBPNG_GIT_TAG v1.6.55)
 
 if(EXISTS "${AVIF_SOURCE_DIR}/ext/zlib")
     message(STATUS "libavif(AVIF_ZLIBPNG=LOCAL): ext/zlib found; using as FetchContent SOURCE_DIR")

ext/zlibpng.cmd

diff --git a/ext/zlibpng.cmd b/ext/zlibpng.cmd
index df8830d..b0137b5 100755
--- a/ext/zlibpng.cmd
+++ b/ext/zlibpng.cmd
@@ -8,4 +8,4 @@
 cd zlib
 git apply --ignore-whitespace ../zlib.patch
 cd ..
-git clone -b v1.6.51 --depth 1 https://github.com/glennrp/libpng.git
+git clone -b v1.6.55 --depth 1 https://github.com/glennrp/libpng.git