0-about.md

Totally untested/unexecuted/improvised workaround borrowing the technique of https://github.com/symfony/symfony/pull/19053/files -- in short, prepend the command with "export FOO=BAR WHIZ=BANG;"

ExternalBatch.diff

diff --git a/Civi/API/ExternalBatch.php b/Civi/API/ExternalBatch.php
index 1ff9282..2e98ad8 100644
--- a/Civi/API/ExternalBatch.php
+++ b/Civi/API/ExternalBatch.php
@@ -184,6 +184,18 @@ class ExternalBatch {
     if (!$php) {
       throw new \CRM_Core_Exception("Failed to locate PHP interpreter.");
     }
+
+    $env = array_merge($this->env, array(
+      'CIVICRM_SETTINGS' => $this->settingsPath,
+    ));
+    if (!empty($env)) {
+      $parts[] = 'export';
+      foreach ($env as $k => $v) {
+        $parts[] = escapeshellarg("$k=$v");
+      }
+      $parts[] = ';';
+    }
+
     $parts[] = $php;
 
     $parts[] = escapeshellarg($this->root . '/bin/cli.php');
@@ -196,10 +208,7 @@ class ExternalBatch {
     }
     $command = implode(" ", $parts);
 
-    $env = array_merge($this->env, array(
-      'CIVICRM_SETTINGS' => $this->settingsPath,
-    ));
-    return new Process($command, $this->root, $env);
+    return new Process($command, $this->root);
   }
 
   /**