Replaces bundled SDL2 with my SDL2 CI, and updates external SDL2
Additionally, reduces all that boilerplate with a common AddCIPackage in
CPMUtil.cmake, currently used by OpenSSL and SDL2. To be used with ffmpeg in the future
Signed-off-by: crueter <crueter@crueter.xyz>
Reviewed-on: #284
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: Shinmegumi <shinmegumi@eden-emu.dev>