png: add libpng port #344

Job	Run time
call-ci / build (armv7a7-imx6ull-evk)	3m 51s
call-ci / build (armv7a9-zynq7000-qemu)	1m 20s
call-ci / build (armv7a9-zynq7000-zedboard)	1m 29s
call-ci / build (armv7a9-zynq7000-zturn)	1m 17s
call-ci / build (armv7m4-stm32l4x6-nucleo)	1m 16s
call-ci / build (armv7m7-imxrt105x-evk)	1m 22s
call-ci / build (armv7m7-imxrt106x-evk)	1m 25s
call-ci / build (armv7m7-imxrt117x-evk)	1m 22s
call-ci / build (armv8r52-mps3an536-qemu)	1m 4s
call-ci / build (armv8m33-mcxn94x-frdm)	1m 11s
call-ci / build (host-generic-pc)	56s
call-ci / build (ia32-generic-pc)	4m 4s
call-ci / build (ia32-generic-qemu)	4m 11s
call-ci / build (riscv64-generic-qemu)	1m 3s
call-ci / build (riscv64-generic-spike)	48s
call-ci / build (sparcv8leon3-generic-qemu)	1m 2s
call-ci / build (sparcv8leon3-gr712rc-board)	1m 4s
call-ci / build (sparcv8leon3-gr716-mimas)	53s
call-ci / build (sparcv8leon3-gr716-mini)	54s
call-ci / test EMU (armv7a9-zynq7000-qemu)	8m 28s
call-ci / test HW (armv7a7-imx6ull-evk)	7m 35s
call-ci / test EMU (host-generic-pc)	1m 4s
call-ci / test HW (armv7m7-imxrt106x-evk)	2m 42s
call-ci / test EMU (ia32-generic-qemu)	6m 46s
call-ci / test HW (armv7m7-imxrt117x-evk)	2m 48s
call-ci / test EMU (riscv64-generic-qemu)	5m 44s
call-ci / test EMU (sparcv8leon3-generic-qemu)	2m 45s
call-ci / test HW (armv7a9-zynq7000-zedboard)	8m 30s
call-ci / test HW (armv7m4-stm32l4x6-nucleo)	11m 45s
call-ci / tests-summary	17s
call-ci / send-notification	0s
	1h 28m 56s

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