Tests: Skip RunCMake.file INSTALL-FOLLOW_SYMLINK_CHAIN case on Cygwin This case was added by commit e3ff7ced63 (file(INSTALL): Add FOLLOW_SYMLINK_CHAIN argument, 2019-05-16, v3.15.0-rc1~103^2). Skip it on Cygwin because it fails due to `foo/../` pairs being flattened away in symlinks.