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Due to the fact how the automake system works it doesn't rebuild already
prebuild files in distcheck. This lead to a bug, where a rebuild of the
documentation was failing because we missed the fact that the files were
missing from the archive.

By adding distrebuildcheck we workaround that issue by running a
maintainer-clean which also removes prebuild files.
Signed-off-by: René Nussbaumer <rn@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>