[CMake] Bug 13251 - failure extracting symbolic links from tarball on Windows

[Kevin Burge]

I'm running into this problem with building an ExternalProject via a tarball:

CMake Error: Problem with archive_write_header(): Can't create '\'

I vote for just writing the original file, so at least the build can
continue.  2.8.10.2 completely stops the build now upon this error.

Thanks,
Kevin