Rebuilding a failed build of a given SHA is not idempotent

[kirillian]

Environment

• OS ALL
• Ruby ALL
• Shiplane 0.1.5

Current behavior

After a failed build, the previous build's data is left in the build directory. It is not an idempotent action to try and rebuild the SHA if you were to correct, say, a configuration problem. Instead, what happens is that certain files (Dockerfile and docker-compose.yml are the known ones) are overwritten and writing over them a second time causes problems that can't be fixed without redownloading the originals.

Expected behavior

Rebuilding a build should be idempotent