Arc land ArcanistUsageException on jenkins

Execute ‘arc land’ command as part our Jenkins pipeline (linux)

steps {
                sshagent(['automation-ssh-key']){   
                    sh '''
                    arc version --
                    arc list --conduit-token $PHAB_API_TOKEN --
                    arc land --preview --onto master --conduit-token $PHAB_API_TOKEN --trace -- 2>&1|cat
                    '''
                }
            }

Version:

16:55:35 + arc version –
16:55:35 arcanist a0c346bf63ecb958b7e37788a32353cfe698187a (28 May 2020)

got the error:

16:55:36 REMOTE Using remote “origin”, the default remote under Git.
16:55:36 >>> [13] (+302) git remote get-url --push -- origin **16:55:36** <<< [13] (+305) <exec> 2,588 us **16:55:36** >>> [14] (+305) <exec> git --version
16:55:36 <<< [14] (+307) 2,400 us
16:55:36 >>> [15] (+308) git status --porcelain=2 -z **16:55:36** <<< [15] (+404) <exec> 96,768 us **16:55:36** >>> [16] (+404) <exec> git rev-parse --verify origin/master
16:55:36 <<< [16] (+408) 3,360 us
16:55:36 >>> [17] (+408) $ git rev-parse --verify 66fe5223da7bba0bdc638ab343a8e31b41bdf4e7
16:55:36 <<< [17] (+411) 3,244 us
16:55:36 FETCH Fetching “origin/master”…
16:55:36 fatal: unable to fork
16:55:36 Usage Exception: Fetch failed! Fix the error and run “arc land” again.
16:55:36
16:55:36 [2021-02-12 00:55:36] EXCEPTION: (ArcanistUsageException) Fetch failed! Fix the error and run “arc land” again. at [/src/land/ArcanistGitLandEngine.php:236]
16:55:36 arcanist(head=master, ref.master=a0c346bf63ec)
16:55:36 #0 ArcanistGitLandEngine::fetchTarget() called at [/src/land/ArcanistGitLandEngine.php:63]
16:55:36 #1 ArcanistGitLandEngine::execute() called at [/src/workflow/ArcanistLandWorkflow.php:263]
16:55:36 #2 ArcanistLandWorkflow::run() called at [/scripts/arcanist.php:411] [Pipeline] }
16:55:36 [ssh-agent] Stopped.

it could be related with: Use passthru to run `git fetch` in `arc land` so password prompts work · phacility/arcanist@d6b1531 · GitHub

// NOTE: Although this output isn’t hugely useful, we need to passthru
// instead of using a subprocess here because git fetch may prompt the
// user to enter a password if they’re fetching over HTTP with basic
// authentication. See T10314.

$err = $api->execPassthru(
‘fetch – %s %s’,
$this->getTargetRemote(),
$this->getTargetOnto());

Pls, advice how to use ‘arc lend’ on Jenkins