Disable parallel builds in the doc/manual directory
Disable parallel builds in the doc/manual directory

Our target for building the gdbus-codegen documentation doesn't work
in parallel and causes race conditions when moving around temporary
files

freedesktop-unofficial-mirror/realmd__realmd,freedesktop-unofficial-mirror/realmd__realmd,freedesktop-unofficial-mirror/realmd__realmd,freedesktop-unofficial-mirror/realmd__realmd