Merge pull request #1357 from msimberg/gdb-cscs-ci

Install GDB in base image for CSCS CI for easier debugging

.gitlab/docker/Dockerfile.spack_base

@@ -15,6 +15,7 @@ RUN apt-get update && apt-get -yqq install --no-install-recommends \
     findutils \
     g++ \
     gcc \
+    gdb \
     git \
     gnupg2 \
     jq \