Supporting native arm builds on OSX by updating SDL to 2.26.0

[Interrupt]

• Upgrades SDL to 2.26.0, and SDL Mixer to 2.6.3
• Fixes OpenGL rendering on OSX, can no longer abuse context switching
• Also fixes the gamma being way too dark when OpenGL is supported

[ftp27]

@Interrupt The changes in this branch are noticeably improved compared to the master branch. However, I would like to address one issue in the build_deps script. Specifically, the seq operation, which is crucial for Mac users, needs to be fixed. You can review my commit addressing this issue at https://github.com/ftp27/systemshock/commit/35acf5ddc55aea837d21290a9de4aa30ea655cc3.

Additionally, there is another problem related to building fluidsynth-lite. I have forked the repository and made the necessary fixes. I hope the owner of the original repository will merge my pull request. However, if you prefer, you can update the link to the repository in the pull request to my fork - https://github.com/ftp27/fluidsynth-lite