CI: Add variables needed for k8s runners

The Kas container needs to use the entrypoint as that is where the user
changes from root to a normal user.

Also set the KUBERNETES_CPU_REQUEST to the variable CPU_REQUEST as this
needs to be tuned per-deployment.

CPU_REQUEST has no value outside of Arm Corp.  Gitlab CI allows for
variables to be overridden by default.  So, we can give it a default
value of NULL/empty and have everything work internally and externally
by default.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>
Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>

.gitlab-ci.yml

@@ -1,5 +1,12 @@
 image: ghcr.io/siemens/kas/kas:latest-release
 
+variables:
+  CPU_REQUEST: ""
+  # These are needed as the k8s executor doesn't respect the container
+  # entrypoint by default
+  FF_USE_LEGACY_KUBERNETES_EXECUTION_STRATEGY: 0
+  FF_KUBERNETES_HONOR_ENTRYPOINT: 1
+
 stages:
   - prep
   - build
@@ -24,6 +31,8 @@ stages:
 # Generalised fragment to do a Kas build
 .build:
   extends: .setup
+  variables:
+    KUBERNETES_CPU_REQUEST: $CPU_REQUEST
   script:
     - KASFILES=$(./ci/jobs-to-kas "$CI_JOB_NAME")
     - kas shell --update --force-checkout $KASFILES -c 'cat conf/*.conf'