I've done a build with -Pdist and I was able to run one of the MR examples after tweaking the the hadoop-config.sh in libexec/ to
The patch is missing this change in the hadoop-config.sh file
Other than that seems OK.
I think we should follow with 2 JIRAs to flatten all submodules under hadoop-mapreduce-project and hadoop-yarn-project modules. Also, to remove <dependencies> sections from the aggregator POMs.