Homebrew is required. Please see http://brew.sh.

The install target is not reliable. If Dooble.app is not copied to
/Applications/Dooble.d during an install, please copy it manually
(sudo cp -r ./Dooble.app /Applications/Dooble_Qt5.d/.).

Developers, please install Qt via the online installer. The products
appear more stable than the ones included with the full installer.
