ci: Reduce the size of artifacts for build-previous-qemu

The build-previous-qemu job is intented to produce a build of the
previous QEMU release for consumption by the migration-compat-*
jobs. Keep only the pieces of the build that are necessary.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20250513133353.23022-4-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>

.gitlab-ci.d/buildtest.yml

@@ -188,12 +188,11 @@ build-previous-qemu:
     when: on_success
     expire_in: 2 days
     paths:
-      - build-previous
-    exclude:
-      - build-previous/**/*.p
-      - build-previous/**/*.a.p
-      - build-previous/**/*.c.o
-      - build-previous/**/*.c.o.d
+      - build-previous/qemu-bundle
+      - build-previous/qemu-system-aarch64
+      - build-previous/qemu-system-x86_64
+      - build-previous/tests/qtest/migration-test
+      - build-previous/scripts
   needs:
     job: amd64-opensuse-leap-container
   variables: