.gitlab-ci.yml: Ensure we compile before we start the main parallel testing

This build can be as fast as 10mins if the ccache matches and there
are few tests.  Therefore put it first as a sentinal.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>

.gitlab-ci.yml

@@ -1,7 +1,17 @@
 # see https://docs.gitlab.com/ce/ci/yaml/README.html for all available options
 
+# Stages explained
+#
+# images: Build the images with the bootstrap script
+# build_first: Build one thing first to find silly errors (fast job)
+#              (don't pay for 35 machines until something compiles)
+# build: The main parallel job
+#              (keep these to 1hour as we are billed per hour)
+# report: Code coverage reporting
+
 stages:
   - images
+  - build_first
   - build
   - report
 
@@ -178,7 +188,10 @@ samba-admem-mit:
 samba-ad-dc-4-mitkrb5:
   extends: .shared_template
 
+# This task is run first to ensure we compile before we start the
+# main run as it is the fastest full compile of Samba.
 samba-fips:
+  stage: build_first
   extends: .shared_template
   image: $SAMBA_CI_CONTAINER_IMAGE_fedora32