Add s390x support to docker images (#1749)

* Add s390x support to docker images

1. add s390x support to docker images `executor`, `executor(slim)`,
   `executor(debug)` and `warmer`. Fixes #1462 and #1665.

2. Address the building issue of dependency `docker-credential-gcr`
   in Dockerfiles. This issue was introduced when recent commits
   in `docker-credential-gcr` removed the Makefile.

Signed-off-by: Kun-Lu <kun.lu@ibm.com>

* Add s390x support to all images except debug image

* Add s390x support to images.yaml

* Fix ld64.so.1 not found issue on s390x

* Add a comment for copying /lib from busybox container on s390x

.github/workflows/images.yaml

@@ -33,14 +33,14 @@ jobs:
         include:
         - image: executor
           dockerfile: ./deploy/Dockerfile
-          platforms: linux/amd64,linux/arm64
+          platforms: linux/amd64,linux/arm64,linux/s390x
           image-name: gcr.io/kaniko-project/executor
           tag: ${{ github.sha }}
           release-tag: latest
 
         - image: executor-debug
           dockerfile: ./deploy/Dockerfile_debug
-          platforms: linux/amd64,linux/arm64
+          platforms: linux/amd64,linux/arm64,linux/s390x
           image-name: gcr.io/kaniko-project/executor
           tag: ${{ github.sha }}-debug
           release_tag: debug
@@ -54,7 +54,7 @@ jobs:
 
         - image: warmer
           dockerfile: ./deploy/Dockerfile_warmer
-          platforms: linux/amd64,linux/arm64
+          platforms: linux/amd64,linux/arm64,linux/s390x
           image-name: gcr.io/kaniko-project/warmer
           tag: ${{ github.sha }}
           release-tag: latest