cmake: Modern way to link against libpng

7 jobs for modern_cmake_png in 3 minutes and 22 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #3908088
build

00:03:22

passed #3908093
build_android

00:00:46

passed #3908089
build_clang_libcpp

00:03:11

passed #3908092
build_clazy

00:02:42

passed #3908091
build_mingw64_fedora

00:01:56

passed #3908090
build_ubuntu_16_04

00:01:44

passed #3908087
clang_format

00:00:52