Move Jenkins post-build tasks to a post{} block

.ci/Jenkinsfile

@@ -51,7 +51,7 @@ def saveArtifacts() {
 def anySuccess = false
 
 pipeline {
-	agent any
+	agent none
 
 	parameters {
 		string(name: 'BUILD_TYPE',
@@ -94,14 +94,10 @@ pipeline {
 				}
 			}
 		}
+	}
 
-		/* This stage has two tasks:
-		   - Trigger downstream jobs if we're on the main job
-		   - Fail this build if all build stages failed
-		   This could be done with two stages and when{} blocks, but then they
-		   would show up separately in the UI (unless JENKINS-44094 happens). */
-		stage('Finish build') {
-			steps {
+	post {
+		always {
 			script {
 				if (env.JOB_BASE_NAME == '86Box-TestBuildPleaseIgnore') {
 					["${env.JOB_BASE_NAME}2"].each {
@@ -133,4 +129,3 @@ pipeline {
 		}
 	}
 }
-}