.gitlab-ci.yml: make sure that the latest git tag is present in EXTRAVERSION

.gitlab-ci.yml

 image: debian:bullseye-slim
 
 build:
-  script:
-    - apt-get update
-    - apt-get --yes install --no-install-recommends gcc-aarch64-linux-gnu build-essential bison flex device-tree-compiler git
-    - cp mntreform-config .config
-    - ./build.sh
+  script: |
+    apt-get update
+    apt-get --yes install --no-install-recommends gcc-aarch64-linux-gnu build-essential bison flex device-tree-compiler git
+    cp mntreform-config .config
+    ./build.sh
+    if git describe >/dev/null 2>&1; then
+      grep --quiet --fixed-strings "EXTRAVERSION = \\ MNT\\ Reform\\ $(git describe --always --tags --abbrev=0)" Makefile
+    fi
   artifacts:
     paths:
       - "flash.bin"