Yanqin Jin 2b060c1498 Use Env::GetChildren() instead of readdir (#6139)
Summary:
For more portability, switch from readdir to Env::GetChildren() in ldb's
manifest_dump subcommand.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6139

Test Plan:
```
$make check
```
Manually check ldb command.

Differential Revision: D18898197

Pulled By: riversand963

fbshipit-source-id: 92afca379e9fbe78ab70b2eb40d127daad8df5e2
2019-12-10 11:49:09 -08:00
..
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