[Jenkinsfile] Change finn build directory

docker/jenkins/Jenkinsfile

@@ -8,6 +8,7 @@ node {
         "FINN_XILINX_PATH=/proj/xbuilds/SWIP/2022.1_0420_0327/installs/lin64",
         "FINN_XILINX_VERSION=2022.1",
         "FINN_DOCKER_TAG=xilinx/finn:jenkins",
+        "FINN_HOST_BUILD_DIR=/scratch/users/finn_ci",
         "PLATFORM_REPO_PATHS=/opt/xilinx/dsa"
     ]){
         parallel firstBranch: {