libpod: Move uses of unix.O_PATH to container_internal_linux.go

The O_PATH flag is a recent addition to the open syscall and is not
present in darwin or in FreeBSD releases before 13.1. The constant is
not present in the FreeBSD version of x/sys/unix since that package
supports FreeBSD 12.3 and later.

[NO NEW TESTS NEEDED]

Signed-off-by: Doug Rabson <dfr@rabson.org>

libpod/container_internal.go

@@ -1545,7 +1545,7 @@ func (c *Container) mountStorage() (_ string, deferredErr error) {
 
 	rootUID, rootGID := c.RootUID(), c.RootGID()
 
-	dirfd, err := unix.Open(mountPoint, unix.O_RDONLY|unix.O_PATH, 0)
+	dirfd, err := openDirectory(mountPoint)
 	if err != nil {
 		return "", fmt.Errorf("open mount point: %w", err)
 	}
@@ -1568,7 +1568,7 @@ func (c *Container) mountStorage() (_ string, deferredErr error) {
 		return "", fmt.Errorf("resolve /etc in the container: %w", err)
 	}
 
-	etcInTheContainerFd, err := unix.Open(etcInTheContainerPath, unix.O_RDONLY|unix.O_PATH, 0)
+	etcInTheContainerFd, err := openDirectory(etcInTheContainerPath)
 	if err != nil {
 		return "", fmt.Errorf("open /etc in the container: %w", err)
 	}

libpod/container_internal_linux.go

@@ -3249,3 +3249,7 @@ func (c *Container) setupRootlessNetwork() error {
 	}
 	return nil
 }
+
+func openDirectory(path string) (fd int, err error) {
+	return unix.Open(path, unix.O_RDONLY|unix.O_PATH, 0)
+}

libpod/container_internal_unsupported.go

@@ -93,3 +93,7 @@ func getLocalhostHostEntry(c *Container) etchosts.HostEntries {
 func isRootlessCgroupSet(cgroup string) bool {
 	return false
 }
+
+func openDirectory(path string) (fd int, err error) {
+	return -1, errors.New("unsupported openDirectory")
+}