fix out-of-context access

.gitlab-ci.yml

 variables:
   # Installer files are located on Zerberus NFS share
-  PETA_RUN_FILE: /global/installers/petalinux-v2019.1-final-installer.run
+  PETA_RUN_FILE: petalinux-v2019.1-final-installer.run
   PETA_VERSION: "2019.1"
 
 stages:
@@ -8,6 +8,8 @@ stages:
 
 build:
   stage: build
+  before_script:
+  - cp /global/installers/${PETA_RUN_FILE} .
   script:
   - docker build --build-arg PETA_VERSION=${PETA_VERSION} --build-arg PETA_RUN_FILE=${PETA_RUN_FILE} -t petalinux:${PETA_VERSION} .
   tags: