Jenkinsfile: Define PIPELINE_VERSION early to fix devroot name

Move the definition of env.PIPELINE_VERSION very early so that the devroot name
setting can make use of it.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

Jenkinsfile

 #!/usr/bin/env groovy
 
+env.PIPELINE_VERSION = VersionNumber(versionNumberString: '${BUILD_DATE_FORMATTED,"yyyyMMdd"}.${BUILDS_TODAY_Z}')
+
 osname = 'apertis'
 
 release = "v2019dev0"
@@ -398,8 +400,7 @@ def buildImages(architecture, type, boards, debosarguments = "", image = true, s
 
             buildenv.inside("--device=/dev/kvm") {
               stage("setup ${architecture} ${type}") {
-                env.PIPELINE_VERSION = VersionNumber(versionNumberString: '${BUILD_DATE_FORMATTED,"yyyyMMdd"}.${BUILDS_TODAY_Z}')
-                  sh ("env ; mkdir -p ${PIPELINE_VERSION}/${architecture}/${type}")
+                sh ("env ; mkdir -p ${PIPELINE_VERSION}/${architecture}/${type}")
               }
 
               // Add successfully build artifacts here to know which ones we need to upload and test