build script that increments the build number after being built

i am having trouble try to get my mod to export mod files with different build number

This is my current build script

buildscript {
    repositories {
        mavenCentral()
        maven {
            name = "forge"
            url = "http://files.minecraftforge.net/maven"
        }
        maven {
            name = "sonatype"
            url = "https://oss.sonatype.org/content/repositories/snapshots/"
        }
    }
    dependencies {
        classpath 'net.minecraftforge.gradle:ForgeGradle:1.2-SNAPSHOT'
    }
}

apply plugin: 'forge'

ext.configFile = file "build.properties"
configFile.withReader{
    def prop = new Properties()
    prop.load(it)
    ext.config = new ConfigSlurper().parse prop
}

ext.buildnumber = 0
if (System.getenv().BUILD_NUMBER)
    project.buildnumber = System.getenv().BUILD_NUMBER
logger.lifecycle "Building Version: " + project.config.buildnumber
project.buildnumber += 1


version = config.mod_version
group= "fergoman123.mods.fergoutil" // http://maven.apache.org/guides/mini/guide-naming-conventions.html
archivesBaseName = "FergoUtil"

minecraft {
    version = config.minecraft_version + "-" + config.forge_version
    assetDir = "eclipse/assets"

    replaceIn "fergoman123/mods/fergoutil/lib/ModInfo.java"
    replace "@mod_version@", project.version
    replace "@mcVersion@", project.config.minecraft_version
    replace "@forge_version@", project.config.forge_version
    replace "@buildNum@", project.buildnumber
}

version = "${config.minecraft_version}-${config.mod_version}-${buildnumber}"

dependencies {
    // you may put jars on which you depend on in ./libs
    // or you may define them like so..
    //compile "some.group:artifact:version:classifier"
    //compile "some.group:artifact:version"
      
    // real examples
    //compile 'com.mod-buildcraft:buildcraft:6.0.8:dev'  // adds buildcraft to the dev env
    //compile 'com.googlecode.efficient-java-matrix-library:ejml:0.24' // adds ejml to the dev env

    // for more info...
    // http://www.gradle.org/docs/current/userguide/artifact_dependencies_tutorial.html
    // http://www.gradle.org/docs/current/userguide/dependency_management.html

}

processResources
{
    // this will ensure that this task is redone when the versions change.
    inputs.property "version", project.version
    inputs.property "mcversion", project.minecraft.version

    // replace stuff in mcmod.info, nothing else
    from(sourceSets.main.resources.srcDirs) {
        include 'mcmod.info'
                
        // replace version and mcversion
        expand 'version':project.config.mod_version, 'mcversion':project.config.mcVersion
    }
        
    // copy everything else, thats not the mcmod.info
    from(sourceSets.main.resources.srcDirs) {
        exclude 'mcmod.info'
    }
}

Any Help is appreciated