workflows/tests: handle system Linuxbrew.

GitHub Actions has started rolling out Linuxbrew to some workers so
ensure we can handle whether or not it's present.

Cleanup and move things around while we're here.

.github/workflows/tests.yml

@@ -19,42 +19,44 @@ jobs:
 
     - name: Set up Homebrew PATH
       run: |
-        if [ "$RUNNER_OS" = "macOS" ]; then
-          echo "::add-path::/usr/local/bin:/usr/bin:/bin"
+        if [ "$RUNNER_OS" = "Linux" ]; then
+          echo "::add-path::/home/linuxbrew/.linuxbrew/bin"
         else
-          echo "::add-path::/home/linuxbrew/.linuxbrew/bin:/usr/bin:/bin"
+          echo "::add-path::/usr/local/bin"
         fi
 
     - name: Set up Homebrew
       run: |
         if [ "$RUNNER_OS" = "Linux" ]; then
           HOMEBREW_REPOSITORY=/home/linuxbrew/.linuxbrew/Homebrew
-          sudo mkdir -p /home/linuxbrew/.linuxbrew
-          cd ..
-          sudo mv "brew" "$HOMEBREW_REPOSITORY"
-          sudo ln -s "$HOMEBREW_REPOSITORY" "brew"
-          cd /home/linuxbrew/.linuxbrew
-          sudo mkdir -p bin etc include lib opt sbin share var/homebrew/linked Cellar
-          sudo ln -s ../Homebrew/bin/brew /home/linuxbrew/.linuxbrew/bin/
-          sudo chown -R "$USER" /home/linuxbrew
 
-          # Install taps needed for 'brew tests'
-          export HOMEBREW_NO_AUTO_UPDATE=1
-          brew tap homebrew/bundle
-        else
-          HOMEBREW_REPOSITORY="$(brew --repo)"
+          sudo mkdir -p "$HOMEBREW_REPOSITORY/Library/Taps"
           mv "$HOMEBREW_REPOSITORY/Library/Taps" "$PWD/Library"
           sudo rm -rf "$HOMEBREW_REPOSITORY"
-          sudo ln -s "$PWD" "$HOMEBREW_REPOSITORY"
-          brew update-reset Library/Taps/homebrew/homebrew-core
+          sudo ln -sf "$PWD" "$HOMEBREW_REPOSITORY"
 
-          # Install taps needed for 'brew tests'
-          export HOMEBREW_NO_AUTO_UPDATE=1
-          brew tap homebrew/cask
-          brew tap homebrew/bundle
-          brew tap homebrew/services
+          cd /home/linuxbrew/.linuxbrew
+          sudo mkdir -p bin etc include lib opt sbin share var/homebrew/linked Cellar
+          sudo ln -sf ../Homebrew/bin/brew /home/linuxbrew/.linuxbrew/bin/
+          sudo chown -R "$USER" /home/linuxbrew
+
+          brew update-reset Homebrew/Library/Taps/homebrew/homebrew-core
+        else
+          HOMEBREW_REPOSITORY="$(brew --repo)"
+
+          mv "$HOMEBREW_REPOSITORY/Library/Taps" "$PWD/Library"
+          sudo rm -rf "$HOMEBREW_REPOSITORY"
+          sudo ln -sf "$PWD" "$HOMEBREW_REPOSITORY"
+
+          brew update-reset Library/Taps/homebrew/homebrew-core
         fi
 
+    - name: Set up Ruby
+      if: matrix.os == 'ubuntu-latest'
+      uses: actions/setup-ruby@v1
+      with:
+        ruby-version: '2.6'
+
     - name: Run brew config
       run: brew config
 
@@ -81,6 +83,17 @@ jobs:
           sudo chmod -R g-w,o-w /home/linuxbrew /home/runner /opt
         fi
 
+    - name: Install taps
+      run: |
+        # Install taps needed for 'brew tests' and 'brew man'
+        export HOMEBREW_NO_AUTO_UPDATE=1
+        sudo chown -R "$USER" Library/Taps
+        brew tap homebrew/bundle
+        brew tap homebrew/services
+        if [ "$RUNNER_OS" = "macOS" ]; then
+          brew tap homebrew/cask
+        fi
+
     - name: Run brew style
       run: brew style --display-cop-names