Semicolon-separated list of directories to be ignored by
find_path() commands. This is useful in cross-compiling
environments where some system directories contain incompatible but
possibly linkable libraries. For example, on cross-compiled cluster
environments, this allows a user to ignore directories containing
libraries meant for the front-end machine.
By default this contains a list of directories containing incompatible
binaries for the host system. See the
that is intended to be set by the project.