Use `ZLIB_ROOT` instead of deprecated `PNG_BUILD_ZLIB` #887

Job	Run time
macos-static (macos-12)	2m 31s
windows-mingw-build (32)	1m 4s
windows-mingw-build (64)	51s
windows (32, windows-2019)	4m 0s
unix (ubuntu-20.04, g++, make)	3m 42s
windows (32, windows-2022)	5m 35s
unix (ubuntu-20.04, g++, cmake)	3m 49s
windows (64, windows-2019)	4m 1s
unix (ubuntu-20.04, clang++, make)	2m 55s
windows (64, windows-2022)	10m 6s
unix (ubuntu-20.04, clang++, cmake)	3m 5s
unix (ubuntu-22.04, g++, make)	3m 50s
unix (ubuntu-22.04, g++, cmake)	3m 49s
unix (ubuntu-22.04, clang++, make)	2m 36s
unix (ubuntu-22.04, clang++, cmake)	2m 37s
unix (macos-11, clang++, make)	10m 28s
unix (macos-11, clang++, cmake)	11m 48s
unix (macos-12, clang++, make)	13m 6s
unix (macos-12, clang++, cmake)	10m 21s
windows-mingw-testing (windows-2019, 32)	3m 39s
windows-mingw-testing (windows-2019, 64)	3m 8s
windows-mingw-testing (windows-2022, 32)	6m 15s
windows-mingw-testing (windows-2022, 64)	4m 31s
	1h 57m 47s

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