Jenkins pipeline: @NonCPS

import com.cloudbees.groovy.cps.NonCPS
import jenkins.model.*
import hudson.model.Result

@NonCPS
def getProject(projectName) {
    // CloudBees folder plugin is supported, you can use natural paths:
    // in a postbuild action use `manager.hudson`
    // in the script web console use `Jenkins.instance`
    def project = jenkins.model.Jenkins.instance.getItemByFullName(projectName)
    if (!project) {error("Project not found: $projectName")}
    return project
}

project = getProject('foo/bar')
build = project.getBuildByNumber(2443)  // build = project.getBuild(project, '2443')

build.@result = hudson.model.Result.SUCCESS
// build.@result = hudson.model.Result.NOT_BUILT
// build.@result = hudson.model.Result.UNSTABLE
// build.@result = hudson.model.Result.FAILURE
// build.@result = hudson.model.Result.ABORTED