cmake: fix build after 3rdparty updates

3rdparty/libpng/CMakeLists.txt

@@ -4,11 +4,6 @@ if (NOT USE_SYSTEM_LIBPNG)
 	# We use libpng's static library and don't need to build the shared library and run the tests
 	set(PNG_SHARED OFF CACHE BOOL "Build shared lib")
 	set(PNG_TESTS OFF CACHE BOOL "Build libpng tests")
-	if (NOT USE_SYSTEM_ZLIB)
-		set(PNG_BUILD_ZLIB ON CACHE BOOL "Custom zlib location, else find_package is used")
-		add_library(ZLIB::ZLIB INTERFACE IMPORTED)
-		target_link_libraries(ZLIB::ZLIB INTERFACE 3rdparty_zlib)
-	endif()
 	set(SKIP_INSTALL_ALL ON)
 	add_subdirectory(libpng EXCLUDE_FROM_ALL)
 	target_include_directories(png_static INTERFACE "${libpng_BINARY_DIR}" "${libpng_SOURCE_DIR}")