Remove CentOS 7 support... (#2305)

...and force all remaining CentOS jobs to use Rocky Linux instead.

This workaround mostly aims at Bazel release branches that contain old
versions of CI configurations. We should remove it after a brief
migration period.

Progress towards
#2272

Author: fweikert

buildkite/bazelci.py

@@ -266,27 +266,6 @@
 # the platform name in a human readable format, and a the buildkite-agent's
 # working directory.
 PLATFORMS = {
-    "centos7": {
-        "name": "CentOS 7",
-        "emoji-name": ":centos: CentOS 7",
-        "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/centos7",
-        "python": "python3.6",
-    },
-    "centos7_java11": {
-        "name": "CentOS 7 (OpenJDK 11, gcc 4.8.5)",
-        "emoji-name": ":centos: CentOS 7 (OpenJDK 11, gcc 4.8.5)",
-        "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/centos7-java11",
-        "python": "python3.6",
-    },
-    "centos7_java11_devtoolset10": {
-        "name": "CentOS 7 (OpenJDK 11, gcc 10.2.1)",
-        "emoji-name": ":centos: CentOS 7 (OpenJDK 11, gcc 10.2.1)",
-        "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/centos7-java11-devtoolset10",
-        "python": "python3.6",
-    },
     "rockylinux8": {
         "name": "Rocky Linux 8",
         "emoji-name": ":rocky: Rocky Linux 8",
@@ -2713,30 +2692,13 @@ def execute_command(
 def create_step(
     label, commands, platform, shards=1, soft_fail=None, concurrency=None, concurrency_group=None
 ):
-    # TODO: remove
-    if "centos" in platform:
-        tmpdir = tempfile.mkdtemp()
-        try:
-            basename = "{}_{}_{}_{}.txt".format(os.getenv("BUILDKITE_ORGANIZATION_SLUG"),
-                os.getenv("BUILDKITE_PIPELINE_SLUG"),
-                os.getenv("BUILDKITE_BUILD_NUMBER"),
-                os.getenv("BUILDKITE_JOB_ID"))
-            path = os.path.join(tmpdir, basename)
-            with open(path, "wt") as f:
-                f.write(platform)
-
-            execute_command(
-                [
-                    gsutil_command(),
-                    "cp",
-                    path,
-                    f"gs://bazel-centos-deprecation/{basename}",
-                ]
-            )
-        except Exception as ex:
-            eprint(ex)
-        finally:
-            shutil.rmtree(tmpdir)
+    # TODO(#2272): remove after a migration period
+    if "centos7" in platform:
+        log_deprecated_platform_usage(platform)
+        # Move all CentOS workloads to Rocky Linux.
+        # A simple "replace" works since our Rocky Linux images
+        # follow the same naming convention as the CentOS ones.
+        platform = platform.replace("centos7", "rockylinux8")
 
     if "docker-image" in PLATFORMS[platform]:
         step = create_docker_step(
@@ -2834,6 +2796,31 @@ def create_docker_step(
     return step
 
 
+def log_deprecated_platform_usage(platform):
+    tmpdir = tempfile.mkdtemp()
+    try:
+        basename = "{}_{}_{}_{}.txt".format(os.getenv("BUILDKITE_ORGANIZATION_SLUG"),
+            os.getenv("BUILDKITE_PIPELINE_SLUG"),
+            os.getenv("BUILDKITE_BUILD_NUMBER"),
+            os.getenv("BUILDKITE_JOB_ID"))
+        path = os.path.join(tmpdir, basename)
+        with open(path, "wt") as f:
+            f.write(platform)
+
+        execute_command(
+            [
+                gsutil_command(),
+                "cp",
+                path,
+                f"gs://bazel-centos-deprecation/{basename}",
+            ]
+        )
+    except Exception as ex:
+        eprint(ex)
+    finally:
+        shutil.rmtree(tmpdir)
+
+
 def print_project_pipeline(
     configs,
     project_name,