macOS: install GNU tar

Author: Jonas Schievink

.github/workflows/ci.yaml

@@ -42,6 +42,12 @@ jobs:
       if: matrix.os == 'windows-latest'
       run: Rename-Item C:\Users\runneradmin\.rustup\toolchains\stable-x86_64-pc-windows-msvc C:\Users\runneradmin\.rustup\toolchains\stable-x86_64-pc-windows-msvc.old
 
+    - name: Install GNU tar
+      if: matrix.os == 'macos-latest'
+      run: |
+        brew install gnu-tar
+        echo PATH="/usr/local/opt/gnu-tar/libexec/gnubin:$PATH" >> $GITHUB_ENV
+
     - name: Install Rust toolchain
       uses: actions-rs/toolchain@v1
       with: