Helm (built docker image) really heavy on cloud build pipeline and affect execution time

## Affected builder image

[**gcr.io/cloud-builders-community/helm**](https://github.com/GoogleCloudPlatform/cloud-builders-community/tree/master/helm)

The image built for helm to be used on cloud build is very (very) heavy, more than 3GB
https://github.com/GoogleCloudPlatform/cloud-builders-community/tree/master/helm

## Expected Behavior

I would like the build to result to a smaller image so the cloud build step can execute faster (as the pull would be less significant)

## Actual Behavior

The image built for helm to be used on cloud build is very (very) heavy, more than 3GB