Script build.sh is for manual run of build.
Common deps libpng, gettext, freetype, gpm, libjep-turbo, joncpp, liboff,
libvorbis, luajit, zstd, sdl2 and curl are downloaded and built
by functions in deps.sh script.
ANGLE is cloned and build by functions in angle.sh script.
BSD 2.0, see LICENSE file when license in not included in file header