Add Opensuse leap 15.6 to CI

.cirrus.yml

@@ -251,6 +251,14 @@ opensuse_leap_15_5_task:
     dockerfile: ci/opensuse-leap-15.5/Dockerfile
     << : *RESOURCES_TEMPLATE
   << : *CI_TEMPLATE
+  << : *SKIP_TASK_ON_PR
+
+opensuse_leap_15_6_task:
+  container:
+    # Opensuse Leap 15.6 EOL: ~Dec 2025
+    dockerfile: ci/opensuse-leap-15.6/Dockerfile
+    << : *RESOURCES_TEMPLATE
+  << : *CI_TEMPLATE
 
 opensuse_tumbleweed_task:
   container:

ci/opensuse-leap-15.6/Dockerfile

@@ -0,0 +1,39 @@
+FROM opensuse/leap:15.6
+
+# A version field to invalidate Cirrus's build cache when needed, as suggested in
+# https://github.com/cirruslabs/cirrus-ci-docs/issues/544#issuecomment-566066822
+ENV DOCKERFILE_VERSION 20230905
+
+RUN zypper addrepo https://download.opensuse.org/repositories/openSUSE:Leap:15.6:Update/standard/openSUSE:Leap:15.6:Update.repo \
+ && zypper refresh \
+ && zypper in -y \
+    bison \
+    ccache \
+    cmake \
+    curl \
+    flex \
+    gcc12 \
+    gcc12-c++ \
+    git \
+    gzip \
+    libopenssl-devel \
+    libpcap-devel \
+    make \
+    openssh \
+    python312 \
+    python312-devel \
+    python312-pip \
+    swig \
+    tar \
+    which \
+    zlib-devel \
+  && rm -rf /var/cache/zypp
+
+RUN update-alternatives --install /usr/bin/pip3 pip3 /usr/bin/pip3.12 100
+RUN update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.12 100
+RUN update-alternatives --install /usr/bin/python3-config python3-config /usr/bin/python3.12-config 100
+
+RUN pip3 install websockets junit2html
+
+RUN update-alternatives --install /usr/bin/cc cc /usr/bin/gcc-12 100
+RUN update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++-12 100