WITH_META_MODE: Disable cookie handling for include installation.

Using a cookie with meta mode causes it to *not rerun* (as normal make
does) unless the command changes or filemon-detected files change.

After all of the work done here it turns out that skipping installation
is dangerous since the install commands use <dir>/*.h. The actual build
command is not changing but the files installed are changing by the mere
act of adding a new header into the source tree. Thus we cannot safely
use meta mode logic here. It must always rerun and install the headers.
The install -C flag at least prevents churning timestamps when
installing a header that was already present.

Sponsored by: EMC / Isilon Storage Division