Before you can build mpv & mpv.app on an Apple silicon Mac, there's a couple of required dependencies you'll need to install if you haven't already:
- 
Go to System Preferences > Software Update. If there's anything there to update, do it. 
- 
If you don't have the Xcode Command Line Tools installed, run xcode-select --installand select Install on the prompt that appears.
- 
If you don't have Homebrew installed, follow the instructions here. 
- 
If you don't have all of mpv's dependencies installed, run brew install --build-from-source --only-dependencies mpv && brew install libplacebo.
You'll also need a local copy of the mpv repo, which you can get by running git clone https://github.com/mpv-player/mpv.
You can now run the attached script to build mpv & mpv.app on an Apple silicon Mac yourself. Just make sure to run it from the root directory of the cloned repo.
If you want to bundle a static build of mpv.app, perform these steps following the ones above.
- 
Run brew install dylibbundler.
- 
Run the script from the root directory of the cloned repo, but append --staticto the command, like./build-mpv_silicon.sh --static.
Going forward, you can update your local copy of the repo by running the following commands from its root directory:
git reset --hard
git clean --force -d -x
git pull origin master
FYI, If you want to enable gpu-next, you have to install the Vulkan SDK https://sdk.lunarg.com/sdk/download/latest/mac/vulkan-sdk.dmg