ci: Introduce a template for upstream QEMU build

This was heavily inspired by QEMU's upstream CI buildtest-template.yml.
Rather than referencing QEMU's template directly (which GitLab can do),
this patch resorts to hard-coding the build steps ourselves, solely
because there's no guarantee QEMU will keep either the template file
name or the template name from which the build steps were mostly copied
from.

Signed-off-by: Erik Skultety <eskultet@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

ci/integration-template.yml

@@ -1,3 +1,22 @@
+.qemu-build-template: &qemu-build-template
+  - git clone --depth 1 https://gitlab.com/qemu-project/qemu.git
+  - cd qemu
+  #
+  # inspired by upstream QEMU's buildtest-template.yml
+  - export JOBS="$(expr $(nproc) + 1)"
+  - mkdir build
+  - cd build
+  - ../configure --prefix=/usr
+                 --enable-werror
+                 --disable-tcg
+                 --disable-docs
+                 --target-list=x86_64-softmmu || (cat config.log meson-logs/meson-log.txt && exit 1)
+  - make -j"$JOBS"
+  - if test -n "$MAKE_CHECK_ARGS";
+    then
+      make -j"$JOBS" check-build;
+    fi
+  - sudo make install
 
 
 .install-deps: &install-deps