parallelize binary builds and add BUILD_IMAGES allow-list

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Prucek

hack/install.sh

@@ -27,6 +27,18 @@ if [[ ${2:-} == "remove-dummy" ]]; then
   rm -f cmd/repo-init/frontend/dist/dummy
 fi
 
+# BUILD_IMAGES is an allow-list: if set, only these binaries are built.
+# SKIPPED_IMAGES is a deny-list: if set, these binaries are skipped.
+# BUILD_IMAGES takes precedence over SKIPPED_IMAGES.
+declare -A build_images_map
+if [[ -n "${BUILD_IMAGES:-}" ]]; then
+  echo "Building only: ${BUILD_IMAGES}"
+  IFS=',' read -ra build_array <<< "${BUILD_IMAGES}"
+  for img in "${build_array[@]}"; do
+    build_images_map["${img}"]=1
+  done
+fi
+
 declare -A skipped_images_map
 if [[ -n "${SKIPPED_IMAGES:-}" ]]; then
   echo "Skipping images: ${SKIPPED_IMAGES}"
@@ -36,11 +48,44 @@ if [[ -n "${SKIPPED_IMAGES:-}" ]]; then
   done
 fi
 
-for dir in $( find ./cmd/ -mindepth 1 -maxdepth 1 -type d -not \( -name '*ipi-deprovison*' \) ); do
+MAX_PARALLEL="${MAX_PARALLEL:-4}"
+pids=()
+failures=()
+
+for dir in $( find ./cmd/ -mindepth 1 -maxdepth 1 -type d -not \( -name '*ipi-deprovison*' \) | sort ); do
     command="$( basename "${dir}" )"
-    if [[ -n "${skipped_images_map[${command}]:-}" ]]; then
-        echo "Skipping install for ${command} (in SKIPPED_IMAGES)"
+
+    # If BUILD_IMAGES is set, only build listed binaries
+    if [[ -n "${BUILD_IMAGES:-}" ]]; then
+      if [[ -z "${build_images_map[${command}]:-}" ]]; then
         continue
+      fi
+    elif [[ -n "${skipped_images_map[${command}]:-}" ]]; then
+      echo "Skipping install for ${command} (in SKIPPED_IMAGES)"
+      continue
+    fi
+
+    echo "Building ${command}..."
+    go install -v $RACE_FLAG -ldflags "-X 'sigs.k8s.io/prow/pkg/version.Name=${command}' -X 'sigs.k8s.io/prow/pkg/version.Version=${version}'" "./cmd/${command}/..." &
+    pids+=($!)
+
+    # Throttle: wait for a slot when we hit the limit
+    if [[ ${#pids[@]} -ge $MAX_PARALLEL ]]; then
+      if ! wait "${pids[0]}"; then
+        failures+=("${pids[0]}")
+      fi
+      pids=("${pids[@]:1}")
+    fi
+done
+
+# Wait for remaining builds
+for pid in "${pids[@]}"; do
+    if ! wait "$pid"; then
+        failures+=("$pid")
     fi
-    go install -v $RACE_FLAG -ldflags "-X 'sigs.k8s.io/prow/pkg/version.Name=${command}' -X 'sigs.k8s.io/prow/pkg/version.Version=${version}'" "./cmd/${command}/..."
 done
+
+if [[ ${#failures[@]} -gt 0 ]]; then
+    echo "ERROR: ${#failures[@]} build(s) failed"
+    exit 1
+fi