tools: one Gradle lock helper (gradle-lock.sh) for gradle-serial.sh and clean-builds.sh

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQd3pEP9UeN2uifbHknQ7B

tools/clean-builds.sh

@@ -5,6 +5,8 @@
 # Prints what it removes and the space freed. Waits for the Gradle lock of tools/gradle-serial.sh, so it never deletes
 # under a running build. The orchestrator runs it after removing a worktree or when the disk is low.
 # Usage from any checkout:  tools/clean-builds.sh [--dry-run]
+# shellcheck source-path=SCRIPTDIR source=gradle-lock.sh
+. "$(dirname "$0")/gradle-lock.sh"
 dry=0
 case "$1" in
   --dry-run) dry=1 ;;
@@ -39,14 +41,8 @@ done > "$list"
 if [ ! -s "$list" ]; then echo "Nothing to remove."; exit 0; fi
 
 if [ "$dry" -eq 0 ]; then
-  lock=/tmp/kvitt-gradle.lock
-  while ! mkdir "$lock" 2>/dev/null; do
-    pid=$(cat "$lock/pid" 2>/dev/null)
-    if [ -n "$pid" ] && ! kill -0 "$pid" 2>/dev/null; then rm -rf "$lock"; continue; fi
-    sleep 5
-  done
-  echo $$ > "$lock/pid"
-  trap 'rm -rf "$lock"; rm -f "$list"' EXIT INT TERM HUP
+  gradle_lock_acquire
+  trap 'rm -rf "$KVITT_GRADLE_LOCK"; rm -f "$list"' EXIT INT TERM HUP
 fi
 
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