Dockerfile: Move ARG statements

Changing the values of an ARG statement will invalidate all following
RUN statements, because the ARGs are passed as environment variables to
the RUN statements.
We move them to where they are actually needed to benefit from unchanged
layers as much as possible.

Change-Id: Ia56e6b1a5a9a75967003dc1ccb43e6d5cc032fc9

docker_image/Dockerfile

@@ -35,12 +35,6 @@ COPY docker-entrypoint.sh /
 # Starts the entrypoint script and hands over CMD by default
 ENTRYPOINT ["/docker-entrypoint.sh"]
 
-# Pure build time variable declarations (docker build --build-arg KEY=val)
-ARG CMK_VERSION="2.5.0b1"
-ARG CMK_EDITION
-# Distro codename is used to find the corresponding .deb package
-ARG DISTRO_CODENAME="jammy"
-
 # Make the list of required packages available to the following command
 COPY needed-packages /needed-packages
 
@@ -76,6 +70,12 @@ RUN set -e \
     && rm -rf /var/lib/apt/lists/* \
     && rm needed-packages
 
+# Pure build time variable declarations (docker build --build-arg KEY=val)
+ARG CMK_VERSION="2.5.0b1"
+ARG CMK_EDITION
+# Distro codename is used to find the corresponding .deb package
+ARG DISTRO_CODENAME="jammy"
+
 # Optionally copy an existing Checkmk debian package to the container. In case the file is
 # available that is later used by the build procedure the file will not be downloaded.
 COPY check-mk-${CMK_EDITION}-${CMK_VERSION}_0.${DISTRO_CODENAME}*.deb Check_MK-pubkey.gpg /