gitlab-ci: run the makefile build on gcc

Use the `gcc:latest` container image to run the GNU makefile ci
job. This has the toolchain installed, and is used by other projects
so should be cached by the runners. Other jobs install the packages
they need on a basic `debian:bookworm-slim` image, testing a different
path.

Author: rillian

.gitlab-ci.yml

@@ -123,6 +123,7 @@ meson arm64:
 
 makefile:
   stage: build
+  image: 'gcc'
   before_script:
     - apt-get update &&
       apt-get install -y zip doxygen git make wget