doc_repo: deps-file: add empty targets
doc_repo: deps-file: add empty targets

Much line gcc with the -MMD option

thiblahute/hotdoc,thiblahute/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc