gitlab: use CI for building website contents

Run the bare minimum build that is possible to create the docs, avoiding
compiling code which other jobs will deal with.

The generated website is published as an artifact and thus is browsable
by developers on build completion and can be downloaded as a zip file.
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

.gitlab-ci.yml

@@ -3,6 +3,7 @@ variables:
   GIT_DEPTH: 100
 
 stages:
+  - prebuild
   - cross_build
 
 
@@ -53,3 +54,25 @@ debian-sid-cross-i686:
 debian-sid-cross-mipsel:
   <<: *cross_build_default_job_definition
   image: quay.io/libvirt/buildenv-libvirt-debian-sid-cross-mipsel:latest
+
+# This artifact published by this job is downloaded by libvirt.org to
+# be deployed to the web root:
+#    https://gitlab.com/libvirt/libvirt/-/jobs/artifacts/master/download?job=website
+website:
+  stage: prebuild
+  script:
+    - mkdir build
+    - cd build
+    - ../autogen.sh --prefix=$(pwd)/../vroot || (cat config.log && exit 1)
+    - $MAKE -j $(getconf _NPROCESSORS_ONLN) -C docs
+    - $MAKE -j $(getconf _NPROCESSORS_ONLN) -C docs install
+    - cd ..
+    - mv vroot/share/doc/libvirt/html/ website
+  image: quay.io/libvirt/buildenv-libvirt-fedora-31:latest
+  artifacts:
+    expose_as: 'Website'
+    name: 'website'
+    when: on_success
+    expire_in: 30 days
+    paths:
+      - website