Fixed build on OpenBSD

This fixes docker/buildx#2772

copy/copy_openbsd.go

@@ -0,0 +1,38 @@
+//go:build openbsd
+// +build openbsd
+
+package fs
+
+import (
+	"io"
+	"os"
+
+	"github.com/pkg/errors"
+	"golang.org/x/sys/unix"
+)
+
+func copyFile(source, target string) error {
+	src, err := os.Open(source)
+	if err != nil {
+		return errors.Wrapf(err, "failed to open source %s", source)
+	}
+	defer src.Close()
+	tgt, err := os.Create(target)
+	if err != nil {
+		return errors.Wrapf(err, "failed to open target %s", target)
+	}
+	defer tgt.Close()
+
+	return copyFileContent(tgt, src)
+}
+
+func copyFileContent(dst, src *os.File) error {
+	buf := bufferPool.Get().(*[]byte)
+	_, err := io.CopyBuffer(dst, src, *buf)
+	bufferPool.Put(buf)
+	return err
+}
+
+func mknod(dst string, mode uint32, rDev int) error {
+	return unix.Mknod(dst, uint32(mode), rDev)
+}

copy/copy_unix.go

@@ -1,5 +1,5 @@
-//go:build solaris || darwin || freebsd
-// +build solaris darwin freebsd
+//go:build solaris || darwin || freebsd || openbsd
+// +build solaris darwin freebsd openbsd
 
 package fs
 

copy/stat_bsd.go

@@ -1,4 +1,4 @@
-// +build darwin freebsd netbsd openbsd
+// +build darwin freebsd netbsd
 
 package fs
 

copy/stat_openbsd.go

@@ -0,0 +1,17 @@
+// +build openbsd
+
+package fs
+
+import (
+	"syscall"
+)
+
+// Returns the last-accessed time
+func StatAtime(st *syscall.Stat_t) syscall.Timespec {
+	return st.Atim
+}
+
+// Returns the last-modified time
+func StatMtime(st *syscall.Stat_t) syscall.Timespec {
+	return st.Mtim
+}