Revert commit 2257deb502 (Cmake: Avoid cycle directory dependencies,
2014-08-22) and add a comment explaining the purpose of the original
code.
The check_library_exists_concat macro is intended to be called multiple
times on a sequence of possibly dependent libraries. Later libraries
may depend on earlier libraries when they are static. They cannot be
safely linked in reverse order on some platforms.
Signed-off-by: Brad King <brad.king@kitware.com>
5f3824a5aa