META MODE: Fix rebuilding of lib/clang/include after clang-tblgen.host is
staged.

None of usr.bin/clang/clang-tblgen or its dependencies need
lib/clang/include, so there is no cyclic dependency here to worry about.
The issue came about because of workarounds to dependencies on clang
being optional.

Without this, the clang-tblgen called during the build would change
after it was staged for the host. This would cause lib/clang/include to
rebuild due to changed build commands.

Sponsored by: EMC / Isilon Storage Division