Fixes decompressor when using -Wshorten-64-to-32 (#2062)
Fixes decompressor when using -Wshorten-64-to-32 (#2062)

Spotted on iOS when building with `-Wshorten-64-to-32` (since `__builtin_expect` returns a `long`).
Cyan4973/zstd,Cyan4973/zstd,Cyan4973/zstd,Cyan4973/zstd,Cyan4973/zstd