Maybe for some reason you don't like using docker build,
you want to be cool and use gcr.io/kaniko-project/executor
if you're not building things in subdirectories,
you're all set.
Else, read on.
cloudbuild.yaml dir: this sets the working directory,
defaults to the project root (/workspace)
kaniko will pick the Dockerfile from here
(if not overridden by the -f flag)
kaniko-project/executor -f: Dockerfile,
defaults to Dockerfile
relative paths are from the cloudbuild working directory
kaniko-project/executor: -c: kaniko build context,
defaults to the project root (/workspace)
also must be an absolute path (?)
to get the equivalent of dir: subdir and docker build .
you need dir: subdir and kaniko-project/executor -c /workspace/subdir