isolate_home: correctly handle subdirectory symlinks to $HOME
isolate_home: correctly handle subdirectory symlinks to $HOME

Remove symlinks that target the $HOME directory (or subdirectories
of this directory) within the current WINEPREFIX C:\users\<user>
directory.
Test for symlinks which are in subdirectories of the current
WINEPREFIX.
Ignore symlinks to files (as before).

Closes: #1905

Winetricks/winetricks,Winetricks/winetricks