Add master CI task for macOS BigSur.

This work is part of #582.

.cirrus.yml

@@ -188,7 +188,7 @@ gcc9_ubuntu_release_task:
       type: text/xml
       format: junit
 
-macos_release_task:
+macos_catalina_task:
   osx_instance:
     image: catalina-base
 
@@ -225,6 +225,43 @@ macos_release_task:
     path: build/spicy-*.tar.gz
     type: application/gzip
 
+macos_big_sur_task:
+  osx_instance:
+    image: big-sur-base
+
+  always:
+    ccache_cache:
+      folder: /tmp/ccache
+      fingerprint_script: echo $CIRRUS_TASK_NAME-$CIRRUS_OS
+
+  environment:
+    CCACHE_DIR: /tmp/ccache
+    CCACHE_COMPRESS: 1
+
+  # Pull tags as well since by default Cirrus CI does not fetch them, but they
+  # are needed for `git describe` used in `scripts/autogen-version`. We also
+  # pull submodules here.
+  update_git_script:
+    - git fetch --tags
+    - git submodule update --recursive --init
+
+  install_dependencies_script:
+    - brew install bison flex cmake ninja python@3.8 sphinx-doc doxygen ccache zeek
+    - pip3 install btest sphinx_rtd_theme
+
+  configure_script:
+    - ./configure --generator=Ninja --with-bison=/usr/local/opt/bison --with-flex=/usr/local/opt/flex --enable-ccache
+  build_script:
+    - ninja -C build all check
+  test_build_script:
+    - (cd tests && btest -j -d)
+  packaging_script:
+    - ninja -C build package
+
+  packages_artifacts:
+    path: build/spicy-*.tar.gz
+    type: application/gzip
+
 zeek_packages_task:
   container:
     dockerfile: ci/Dockerfile.packages
@@ -375,7 +412,7 @@ docker_centos_8_task:
     path: build/spicy-*.tar.gz
     type: application/gzip
 
-validate_homebrew_task:
+homebrew_catalina_task:
   only_if: $CIRRUS_BRANCH == 'master'
 
   osx_instance:
@@ -386,6 +423,17 @@ validate_homebrew_task:
   - brew install spicy --HEAD
   - brew test spicy
 
+homebrew_big_sur_task:
+  only_if: $CIRRUS_BRANCH == 'master'
+
+  osx_instance:
+    image: big-sur-base
+
+  script:
+  - brew tap zeek/zeek
+  - brew install spicy --HEAD
+  - brew test spicy
+
 docker_debian9_task:
   only_if: $CIRRUS_BRANCH == 'master'
   container: