Add missing simple documentation for how to use JIB on Google Cloud Build in README

[vorburger]

Background: I'm looking into https://github.com/vorburger/www.fineract.dev/issues/11 and need to convert a Google Cloud Build YAML configuration which used to "just work" for an open source project which used to have a Dockerfile and was switched to JIB by a contributor.

In an ideal world, it would be neat if I could just Ctrl-F for "Google Cloud Build" on the JIB README and it would tell me what I need to do.

Would you accept to review and merge a Pull Request with some addendum to the doc for this?

[vorburger]

It seems like nowadaways this is as simple as shown e.g. in https://github.com/GoogleCloudPlatform/air-draw-demo/blob/master/cloudbuild.yaml? That seems wortwhile (even only very succintly) mentioning on the README.

[vorburger]

The non-availability of gcr.io/cloud-builders/javac:17 (nor :11, only :8) can be a "show stopper" for using JIB from Google Cloud Build for some projects.

[vorburger]

The non-availability of gcr.io/cloud-builders/javac:17 (nor :11, only :8) can be a "show stopper" for using JIB from Google Cloud Build for some projects.

This is wrong, as per this discussion, one CAN use other Java container images.

But a ./gradlew in gcr.io/distroless/java17-debian11:debug fails with:

Step #1: standard_init_linux.go:228: exec user process caused: no such file or directory

but using (e.g.) docker.io/library/eclipse-temurin:17 for https://hub.docker.com/_/eclipse-temurin/ from https://adoptium.net works, as do presumably a number of other JDK container images, such as azul/zulu-openjdk-alpine:17 (not tested).

Would a PR with something about this added to the README be welcome?

@jamesward FYI

[jamesward]

Oh, right. I forgot that the distroless images are based on busybox so you have to do something like:

  - id: 'test'
    name: 'gcr.io/distroless/java:8-debug'
    entrypoint: '/busybox/sh'
    args:
      - -c
      - |
        ln -s /busybox/sh /bin/sh
        ./gradlew --console=plain --no-daemon --gradle-user-home=/home/.gradle test

Or maybe:

- id: 'build-image'
    name: 'gcr.io/distroless/java:8-debug'
    entrypoint: '/busybox/sh'
    args:
      - -c
      - |
        ln -s /busybox/env /usr/bin/env
        /workspace/gradlew --console=plain --no-daemon --gradle-user-home=/home/.gradle bootBuildImage --imageName=gcr.io/$PROJECT_ID/$REPO_NAME:$COMMIT_SHA

A non-Jib example that might be helpful: https://github.com/jamesward/spring-kotlin-postgres/blob/c50c5cdff58970c2fb6249a020e2eb8136478ef3/cloudbuild.yaml

[meltsufin]

@vorburger Please let us know or contribute the documentation update once you test out the suggested options. Thanks!