update ncruces/go-sqlite3 to v0.21.2 (#3626)

vendor/github.com/ncruces/go-sqlite3/internal/dotlk/dotlk_unix.go

@@ -0,0 +1,50 @@
+//go:build unix
+
+package dotlk
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"strconv"
+
+	"golang.org/x/sys/unix"
+)
+
+// TryLock returns nil if it acquired the lock,
+// fs.ErrExist if another process has the lock.
+func TryLock(name string) error {
+	for retry := true; retry; retry = false {
+		f, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
+		if err == nil {
+			f.WriteString(strconv.Itoa(os.Getpid()))
+			f.Close()
+			return nil
+		}
+		if !errors.Is(err, fs.ErrExist) {
+			return err
+		}
+		if !removeStale(name) {
+			break
+		}
+	}
+	return fs.ErrExist
+}
+
+func removeStale(name string) bool {
+	buf, err := os.ReadFile(name)
+	if err != nil {
+		return errors.Is(err, fs.ErrNotExist)
+	}
+
+	pid, err := strconv.Atoi(string(buf))
+	if err != nil {
+		return false
+	}
+	if unix.Kill(pid, 0) == nil {
+		return false
+	}
+
+	err = os.Remove(name)
+	return err == nil || errors.Is(err, fs.ErrNotExist)
+}