win32: only count subdirectories if necessary

Commit 7fb95a2a5 (win32: try to get link count for directories)
allowed stat(2) to report accurate values of st_nlink for
directories.

There are only a couple of places in busybox-w32 where these values
are required.  Disable counting of subdirectories by default and
only enable it when necessary.

Microsoft kindly provide directories to test edge cases like this:

   C:/Windows/WinSxS           (contains many subdirectories)
   C:/Windows/WinSxS/Manifests (contains many files)

Adds 84-112 bytes.

0 files changed, 0 insertions, 0 deletions