message: Make the directories before trying to compress them.
diff: if [[ $TRAVIS_OS_NAME == "windows" && ! -d "/c/Program Files/Epic Games/UE_4.26" ]]
  then
  # Enable compression because disk space is limited on Travis.
  + mkdir "C:\Program Files\Epic Games"
  compact //c "//s:C:\Program Files\Epic Games"
  + mkdir "C:\Program Files (x86)\Epic Games"
  compact //c "//s:C:\Program Files (x86)\Epic Games"
  AWS_ACCESS_KEY_ID=${GOOGLE_ACCESS_KEY_ID} AWS_SECRET_ACCESS_KEY=${GOOGLE_SECRET_ACCESS_KEY} aws s3 --endpoint-url https://storage.googleapis.com cp s3://cesium-unreal-engine/windows-2021-05-07/UE_4.26.zip .
  7z x UE_4.26.zip "-oC:\Program Files\Epic Games"
  