Symbolic link bug in recent Cygwin DLL build

[Mark Geisert]

After installing a recent DLL built from the git source tree I noticed:

~ ln -s /tmp/foo .

~ ls -l foo
lrwxrwxrwx 1 Mark None 12 Apr 15 23:44 foo -> /mnt/tmp/foo

Creating a symbolic link from a different directory adds "/mnt" to the 
path stored in the link.  I don't have a /mnt, env var 'CYGWIN' is empty, 
nothing unusual in /etc/fstab or 'mount' output.  Win 10 v1909.

..mark