Add macos-11 runner to examples job

All examples are already using 21.11 nixpkgs, so that shouldn't prevent
them from working on Big Sur.

Python example is broken because of #186 and Rust one because of #187,
so skip them for now.

Fixes #176

.github/workflows/workflow.yaml

@@ -36,6 +36,7 @@ jobs:
       matrix:
         os: 
           - ubuntu-latest # TODO: this job does not yet work on any version of macOS
+          - macos-11
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2.4.0
@@ -56,6 +57,18 @@ jobs:
           for dir in *; do
               cd "$dir"
               echo
+              if [ "${{ runner.os }}" == "macOS" ]; then
+                case "$dir" in
+                  # Python - https://github.com/tweag/rules_nixpkgs/issues/186
+                  # Rust - https://github.com/tweag/rules_nixpkgs/issues/187
+                  python | \
+                  rust )
+                    echo Skipping $(head -n1 README.md) with Nix
+                    cd ..
+                    continue
+                    ;;
+                esac
+              fi
               echo Running $(head -n1 README.md) with Nix
               nix-shell --command 'bazel run --config=nix :hello'
               # TODO: all toolchains should run without Nixpkgs
@@ -64,6 +77,18 @@ jobs:
           for dir in cc go rust; do
               cd "$dir"
               echo
+              if [ "${{ runner.os }}" == "macOS" ]; then
+                case "$dir" in
+                  # Python - https://github.com/tweag/rules_nixpkgs/issues/186
+                  # Rust - https://github.com/tweag/rules_nixpkgs/issues/187
+                  python | \
+                  rust )
+                    echo Skipping $(head -n1 README.md) without Nix
+                    cd ..
+                    continue
+                    ;;
+                esac
+              fi
               echo Running $(head -n1 README.md) without Nix
               bazel run :hello
               cd ..