build: support -race in binaries

Since a few releases, Go supports `go build -race` and then produces
binaries which do data race detection when invoked. Some changes are needed to
enable using this in a kind cluster:

- `-race` must be passed when building dynamically linked binaries.
  Only those support -race because CGO is required.
  To avoid adding yet another env variables, the existing KUBE_RACE
  gets used to convey the intent.
- KUBE_RACE must be passed into the dockerized build.
- Logging the base image of a release image makes it easier
  to figure out whether the binary has a chance to run.

The base image is important because dynamically linked binaries need a base
image with libc. By default, control plane components are linked statically,
so users need to explicitly override the defaults:

    KUBE_RACE=-race KUBE_CGO_OVERRIDES="kube-apiserver kube-controller-manager kube-scheduler" KUBE_GORUNNER_IMAGE=gcr.io/k8s-staging-test-infra/kubekins-e2e:v20250815-171060767f-master kind build node-image ...

KUBE_GORUNNER_IMAGE changes the base image for kube-apiserver,
kube-controller-manager and kube-scheduler. The kubekins image was picked for
this example because a Prow job definition already uses it. Reusing
it in a job avoids the need to maintain another image definition.

Running conformance tests against such a cluster with alpha+beta features
enabled revealed one new data race:

    $ kubectl logs -n kube-system kube-controller-manager-kind-control-plane
    ...
    WARNING: DATA RACE
    Write at 0x00c00019a730 by goroutine 216:
    k8s.io/client-go/tools/leaderelection.(*LeaderElector).setObservedRecord()
         k8s.io/client-go/tools/leaderelection/leaderelection.go:529 +0x179
    k8s.io/client-go/tools/leaderelection.(*LeaderElector).tryCoordinatedRenew()
         k8s.io/client-go/tools/leaderelection/leaderelection.go:367 +0x5ca
    ...

build/common.sh

@@ -540,6 +540,7 @@ function kube::build::run_build_command_ex() {
     --env "KUBE_BUILD_PLATFORMS=${KUBE_BUILD_PLATFORMS:-}"
     --env "KUBE_CGO_OVERRIDES=' ${KUBE_CGO_OVERRIDES[*]:-} '"
     --env "KUBE_STATIC_OVERRIDES=' ${KUBE_STATIC_OVERRIDES[*]:-} '"
+    --env "KUBE_RACE=${KUBE_RACE:-}"
     --env "FORCE_HOST_GO=${FORCE_HOST_GO:-}"
     --env "GO_VERSION=${GO_VERSION:-}"
     --env "GOTOOLCHAIN=${GOTOOLCHAIN:-}"

build/lib/release.sh

@@ -332,7 +332,7 @@ function kube::release::create_docker_images_for_server() {
           docker_file_path="${KUBE_ROOT}/build/server-image/${binary_name}/Dockerfile"
       fi
 
-      kube::log::status "Starting docker build for image: ${binary_name}-${arch}"
+      kube::log::status "Starting docker build for image: ${binary_name}-${arch} with base ${base_image}"
       (
         rm -rf "${docker_build_path}"
         mkdir -p "${docker_build_path}"

hack/lib/golang.sh

@@ -836,7 +836,7 @@ kube::golang::build_binaries_for_platform() {
       kube::log::info "    ${binary} (static)"
     else
       nonstatics+=("${binary}")
-      kube::log::info "    ${binary} (non-static)"
+      kube::log::info "    ${binary} (non-static${KUBE_RACE:+, race detection})"
     fi
    done
 
@@ -862,6 +862,9 @@ kube::golang::build_binaries_for_platform() {
       -ldflags="${goldflags}"
       -tags="${gotags:-}"
     )
+    if [[ -n "${KUBE_RACE:-}" ]]; then
+        build_args+=("${KUBE_RACE}")
+    fi
     kube::golang::build_some_binaries "${nonstatics[@]}"
   fi