Currently, libpng supports three different types of build automation:
the GNU autotools, CMake, and a legacy of hand-made makefiles.
In order to simplify the continous integration of all of the above
build options, we introduce the following scripts:
* ci_autotools.sh: CI utility for the Autotools build
* ci_cmake.sh: CI utility for the CMake build
* ci_legacy.sh: CI utility for the legacy makefiles
