- Use msbuild where possible for building UAT by checking for mono5
- Hash state of UAT scritps post-compile to skip redundant rebuilds
#jira nojira
#rb na
#ROBOMERGE-OWNER: ben.marsh
#ROBOMERGE-AUTHOR: andrew.grant
#ROBOMERGE-SOURCE: CL 7634479 in //UE4/Release-4.23/... via CL 7634480
#ROBOMERGE-BOT: BUILD (Main -> Dev-Build) (v385-7708028)
[CL 7731875 by andrew grant in Dev-Build branch]