Use thread-safe strerror_r() to get error message (#8087)

Summary:
`strerror()` is not thread-safe, using `strerror_r()` instead. The API could be different on the different platforms, used the code from https://github.com/facebook/folly/blob/0deef031cb8aab76dc7e736f8b7c22d701d5f36b/folly/String.cpp#L457

Pull Request resolved: facebook/rocksdb#8087

Reviewed By: mrambacher

Differential Revision: D27267151

Pulled By: jay-zhuang

fbshipit-source-id: 4b8856d1ec069d5f239b764750682c56e5be9ddb
Signed-off-by: Changlong Chen <levisonchen@live.cn>

env/fs_posix.cc

@@ -862,7 +862,7 @@ class PosixFileSystem : public FileSystem {
     char the_path[256];
     char* ret = getcwd(the_path, 256);
     if (ret == nullptr) {
-      return IOStatus::IOError(strerror(errno));
+      return IOStatus::IOError(errnoStr(errno).c_str());
     }
 
     *output_path = ret;