I hope this fixes a Luke Dashjr coreutils bug report about ext4
ramdisks; see “9.1: du Aborted (corrupt filesystem)”
<https://debbugs.gnu.org/59821>.
* lib/fts.c (fts_build): Fix two bugs. First, fts_stat was being
called without checking its return value, causing a later abort.
Second, there was a race between opening a directory and statting
it, fixed by using fstat on the file descriptor rather than
fstatat on the directory name.