file-cache-find-command-posix-flag

file-cache-find-command-posix-flag is a variable defined in `filecache.el'.
Its value is

not-defined

Documentation:
Set to t, if `file-cache-find-command' handles wildcards POSIX style.
This variable is automatically set to nil or non-nil
if it has the initial value `not-defined' whenever you first
call the `file-cache-add-directory-using-find'.

Under Windows operating system where Cygwin is available, this value
should be t.

You can customize this variable.