Automatically grabs and compiles libpng, and avoids having hacky lines in our Makefile
(the compiler specification *should* be orthogonal to the build target!)
Also move the MinGW package install to the `install_deps.sh` script,
to move logic off of the YAML.
- Updates `actions/checkout` from 4 to 6
- Updates `docker/login-action` from 3 to 4
- Updates `Chizkiyahu/delete-untagged-ghcr-action` from 5 to 6
- Updates `actions/upload-artifact` from 4 to 7
- Updates `actions/download-artifact` from 4 to 8
- Updates `cygwin/cygwin-install-action` from 4 to 6
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>