Oh bah, just set the env vars for git to be happy

Jenkinsfile

@@ -8,8 +8,14 @@ pipeline {
     }
 
     // Run on executors with the "docker" label, because it's either that or Windows here.
-    agent label:"docker && !spinach"
+    agent label:"docker"
 
+    // Make sure we have GIT_COMMITTER_NAME and GIT_COMMITTER_EMAIL set due to machine weirdness.
+    environment {
+        GIT_COMMITTER_NAME = "jenkins"
+        GIT_COMMITTER_EMAIL = "jenkins@jenkins.io"
+    }
+
     // The order that sections are specified doesn't matter - this will still be run
     // after the stages, even though it's specified before the stages.
     postBuild {