v1.5.7
https://github.com/facebook/zstd/releases/tag/v1.5.7

To update the code in the future, follow these steps:
1. Download the source code tarball from https://github.com/facebook/zstd/releases/
2. Delete existing files in 'src/native/external/zstd/'
3. Extract and copy the 'lib' and 'build' directories into 'src/native/external/zstd/'
4. Build and run tests

Only the 'lib' and 'build' directories from the original source were included to minimize unnecessary code.

Current source code has the following patches applied on top of the v.1.5.7 release:

Apply https://github.com/facebook/zstd/commit/0d1f8de9addeb2fcb53f1a6a68ef4ac505253c0e
Apply https://github.com/facebook/zstd/commit/ebfa660b8297170fb0742ac8959aa64940292853
Apply https://github.com/facebook/zstd/commit/23dae4bf49a8b36ab88509c85137b49f74bbc76d

None of the above should be necessary when upgrading to a future version.