Only set BOB_PREFIX_PATH if not set by caller

gitlab/functions.sh

@@ -218,7 +218,10 @@ else
 fi
 
 PYVER=py$(echo ${PYTHON_VERSION} | tr -d '.')
-BOB_PREFIX_PATH=${CONDA_FOLDER}/envs/bob-devel-${PYVER}
+if [ -z "${BOB_PREFIX_PATH}" ]; then
+  # Default on stock installations for our CIs
+  BOB_PREFIX_PATH=${CONDA_FOLDER}/envs/bob-devel-${PYVER}
+fi
 LD_LIBRARY_PATH=${BOB_PREFIX_PATH}/lib
 
 if [ -z "${PYPISERVER}" ]; then