build: fix out-of-tree build broken with 0b04ed5 (#184)
build: fix out-of-tree build broken with 0b04ed5 (#184)

Generating the man pages definitely doesn't depend on existence of
(possibly generated) header files that we omit anyway.

kgaillot/libqb,ClusterLabs/libqb,ClusterLabs/libqb,kgaillot/libqb,ClusterLabs/libqb,kgaillot/libqb