prow: Build minimal arm64 payload

The arm64 payload only contains the following four images which are
the minimal requirements for scheduling Prow builds on an arm64 build
farm:
- clonerefs
- entrypoint
- initupload
- sidecar

The arm64 images will be tagged with an additional `-arm64` suffix.

prow/BUILD.bazel

@@ -2,60 +2,70 @@ package(default_visibility = ["//visibility:public"])
 
 load("@io_bazel_rules_docker//container:bundle.bzl", "container_bundle")
 load("@io_bazel_rules_docker//contrib:push-all.bzl", "docker_push")
-load("//prow:def.bzl", "prefix", "prow_push", "tags")
+load("//prow:def.bzl", "prefix", "prow_push", "tags", "tags_arm64", "dict_union")
 load("//def:image.bzl", image_tags = "tags")
 
 prow_push(
     name = "release-push",
     bundle_name = "release",
-    images = tags(
-        cmds = [
-            "admission",
-            "autobump",
-            "branchprotector",
-            "checkconfig",
-            "clonerefs",
-            "config-bootstrapper",
-            "deck",
-            "entrypoint",
-            "exporter",
-            "gerrit",
-            "crier",
-            "generic-autobumper",
-            "grandmatriarch",
-            "gcsupload",
-            "hook",
-            "hmac",
-            "horologium",
-            "initupload",
-            "invitations-accepter",
-            "jenkins-operator",
-            "mkpj",
-            "mkpod",
-            "peribolos",
-            "sidecar",
-            "sinker",
-            "status-reconciler",
-            "sub",
-            "tide",
-            "tot",
-            "pipeline",
-            "prow-controller-manager",
-        ],
-        targets = {
-            "needs-rebase": "//prow/external-plugins/needs-rebase:image",
-            "cherrypicker": "//prow/external-plugins/cherrypicker:image",
-            "refresh": "//prow/external-plugins/refresh:image",
-            "ghproxy": "//ghproxy:image",
-            "label_sync": "//label_sync:image",
-            "commenter": "//robots/commenter:image",
-            "pr-creator": "//robots/pr-creator:image",
-            "issue-creator": "//robots/issue-creator:image",
-            "configurator": "//testgrid/cmd/configurator:image",
-            "transfigure": "//testgrid/cmd/transfigure:image",
-            "gcsweb": "//gcsweb/cmd/gcsweb:image",
-            "bumpmonitoring": "//experiment/bumpmonitoring:image",
-        },
+    images = dict_union(
+        tags(
+            cmds = [
+                "admission",
+                "autobump",
+                "branchprotector",
+                "checkconfig",
+                "clonerefs",
+                "config-bootstrapper",
+                "deck",
+                "entrypoint",
+                "exporter",
+                "gerrit",
+                "crier",
+                "generic-autobumper",
+                "grandmatriarch",
+                "gcsupload",
+                "hook",
+                "hmac",
+                "horologium",
+                "initupload",
+                "invitations-accepter",
+                "jenkins-operator",
+                "mkpj",
+                "mkpod",
+                "peribolos",
+                "sidecar",
+                "sinker",
+                "status-reconciler",
+                "sub",
+                "tide",
+                "tot",
+                "pipeline",
+                "prow-controller-manager",
+            ],
+            targets = {
+                "needs-rebase": "//prow/external-plugins/needs-rebase:image",
+                "cherrypicker": "//prow/external-plugins/cherrypicker:image",
+                "refresh": "//prow/external-plugins/refresh:image",
+                "ghproxy": "//ghproxy:image",
+                "label_sync": "//label_sync:image",
+                "commenter": "//robots/commenter:image",
+                "pr-creator": "//robots/pr-creator:image",
+                "issue-creator": "//robots/issue-creator:image",
+                "configurator": "//testgrid/cmd/configurator:image",
+                "transfigure": "//testgrid/cmd/transfigure:image",
+                "gcsweb": "//gcsweb/cmd/gcsweb:image",
+                "bumpmonitoring": "//experiment/bumpmonitoring:image",
+            },
+        ),
+        tags_arm64(
+            cmds = [
+                "clonerefs",
+                "entrypoint",
+                "initupload",
+                "sidecar",
+            ],
+        ),
     ),
 )
 
@@ -190,3 +200,4 @@ filegroup(
     ],
     tags = ["automanaged"],
 )
+

prow/cmd/clonerefs/BUILD.bazel

@@ -26,6 +26,8 @@ go_binary(
 prow_image(
     name = "image",
     base = "@git-base//image",
+    base_arm64 = "@git-base-arm64//image",
+    build_arm64 = True,
     component = NAME,
     files = [
         "github_known_hosts",

prow/cmd/entrypoint/BUILD.bazel

@@ -26,6 +26,8 @@ go_binary(
 prow_image(
     name = "image",
     base = "@git-base//image",
+    base_arm64 = "@git-base-arm64//image",
+    build_arm64 = True,
     component = NAME,
     symlinks = {"/entrypoint": "/app/prow/cmd/entrypoint/app.binary"},
     visibility = ["//visibility:public"],

prow/cmd/initupload/BUILD.bazel

@@ -26,6 +26,8 @@ go_binary(
 prow_image(
     name = "image",
     base = "@alpine-base//image",
+    base_arm64 = "@git-base-arm64//image",
+    build_arm64 = True,
     component = NAME,
     symlinks = {"/initupload": "/app/prow/cmd/initupload/app.binary"},
     visibility = ["//visibility:public"],

prow/cmd/sidecar/BUILD.bazel

@@ -26,6 +26,8 @@ go_binary(
 prow_image(
     name = "image",
     base = "@git-base//image",
+    base_arm64 = "@git-base-arm64//image",
+    build_arm64 = True,
     component = NAME,
     symlinks = {"/sidecar": "/app/prow/cmd/sidecar/app.binary"},
     visibility = ["//visibility:public"],

prow/def.bzl

@@ -238,3 +238,9 @@ def release(name, *components):
         name = name,
         objects = objs,
     )
+
+def dict_union(x, y):
+   z = {}
+   z.update(x)
+   z.update(y)
+   return z