fdopendir listed the directory from its first entry whatever position the
descriptor had, and left FD_CLOEXEC unchanged. FreeBSD 11.4 fdopendir sets
FD_CLOEXEC on the descriptor and preserves the initial seek position (lib/libc/gen/opendir.c).
The Windows directory handle now skips the entries the descriptor already
consumed, the Linux handle duplicates the descriptor, and the test requires both.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>