scripts/ci: add libslirp-devel to build-environment

Without libslip enabled we won't have user networking which means the
KVM tests won't run.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230315174331.2959-4-alex.bennee@linaro.org>

scripts/ci/org.centos/stream/8/build-environment.yml

@@ -55,6 +55,7 @@
           - librados-devel
           - librbd-devel
           - libseccomp-devel
+          - libslirp-devel
           - libssh-devel
           - libxkbcommon-devel
           - lzo-devel