Add Jenkinsfile with build stage (#112)

* Add Jenkinsfile with build stage

* Fix the syntax error of Jenkinsfile

* Use steps to wrap container dsl

* Change agent label to golang-1.12

Jenkinsfile

+pipeline {
+    agent {
+        label 'golang-1.12'
+    }
+
+    stages {
+        stage('Build') {
+            parallel {
+                stage('MacOS') {
+                    steps {
+                        container('golang') {
+                            sh label: 'make darwin', script: 'make darwin'
+                        }
+                    }
+                }
+                stage('Linux') {
+                    steps {
+                        container('golang') {
+                            sh label: 'make linux', script: 'make linux'
+                        }
+                    }
+                }
+                stage('Windows') {
+                    steps {
+                        container('golang') {
+                            sh label: 'make win', script: 'make win'
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
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