Serialize the singleton kind fixture across worktrees

tests/kind/lib.sh

@@ -6,6 +6,8 @@ TESTBED="$ROOT/tests/kind"
 RUNTIME="$TESTBED/.runtime"
 BIN="$RUNTIME/bin"
 KUBECONFIG_PATH="$RUNTIME/kubeconfig"
+FIXTURE_LOCK_DIR="${XDG_RUNTIME_DIR:-/tmp/remora-$(id -u)}"
+FIXTURE_LOCK_PATH="$FIXTURE_LOCK_DIR/remora-testbed-kind.lock"
 CONTEXT=kind-remora-testbed
 CLUSTER=remora-testbed
 NERDCTL_NAMESPACE=remora-wp02
@@ -69,8 +71,8 @@ prepare_provider() {
 }
 
 acquire_fixture_lock() {
-  mkdir -p "$RUNTIME"
-  exec 9>"$RUNTIME/fixture.lock"
+  mkdir -p "$RUNTIME" "$FIXTURE_LOCK_DIR"
+  exec 9>"$FIXTURE_LOCK_PATH"
   if ! flock --nonblock 9; then
     printf 'kind test fixture is already in use\n' >&2
     return 1