add jenkinsfile, build number

Jenkinsfile

@@ -0,0 +1,15 @@
+node {
+   stage 'Checkout'
+
+   git url: 'https://github.com/FabricMC/pomf.git'
+
+   stage 'Build'
+
+   sh "rm -rf build/libs/"
+   sh "chmod +x gradlew"
+   sh "./gradlew build"
+
+   stage "Archive artifacts"
+
+   archive 'build/libs/*'
+}

build.gradle

@@ -14,6 +14,13 @@ buildscript {
 }
 
 def minecraft_version = "16w33a"
+def pomfVersion = "${minecraft_version}"
+
+def ENV = System.getenv()
+
+if (ENV.BUILD_NUMBER) {
+    pomfVersion = pomfVersion + "." + "${System.getenv().BUILD_NUMBER}"
+}
 
 import groovy.json.JsonSlurper
 import org.apache.commons.io.FileUtils
@@ -125,6 +132,6 @@ tasks.pomf.dependsOn "setupPomf"
 task build(type: Zip) {
 	from "mappings/"
 	include "**/*"
-	archiveName "pomf-enigma-${minecraft_version}.zip"
+	archiveName "pomf-enigma-${pomfVersion}.zip"
 	destinationDir(file("build/libs"))
-}
+}