cleanup mac build CI job

.github/workflows/test.yaml

@@ -75,8 +75,8 @@ jobs:
     - name: Brew link restored dependencies
       if: steps.dependency-cache.outputs.cache-hit == 'true'
       run: |
-        while read package; do
-          brew link --force "$package" # `--force` for keg-only packages
+        while read pkg; do
+          brew link --force "$pkg" # `--force` for keg-only packages
         done < ~/github_brew_cache_entries.txt
     - name: Install dependencies
       run: ./tools/mac_setup.sh
@@ -85,20 +85,14 @@ jobs:
     - name: Remove pre-existing Homebrew packages for caching
       if: steps.dependency-cache.outputs.cache-hit != 'true'
       run: |
-        new_cellar=$(ls -1 /usr/local/Cellar)
-        comm -12 <(echo "$EXISTING_CELLAR") <(echo "$new_cellar") | while read dir; do
-          if [[ $dir != "zstd" ]]; then # caching step needs zstd
-            echo "Removing /usr/local/Cellar/$dir"
-            rm -rf "/usr/local/Cellar/$dir"
+        cd /usr/local/Cellar
+        new_cellar=$(ls -1)
+        comm -12 <(echo "$EXISTING_CELLAR") <(echo "$new_cellar") | while read pkg; do
+          if [[ $pkg != "zstd" ]]; then # caching step needs zstd
+            rm -rf "$pkg"
           fi
         done
 
-        printf "\n\nNewly installed packages:\n"
-        comm -13 <(echo "$EXISTING_CELLAR") <(echo "$new_cellar") | tee ~/github_brew_cache_entries.txt
-
-        printf "\n\nThe following will be cached:\n"
-        (du -shc /usr/local/Cellar/* | sort -h) || true
-
   build_webcam:
     name: build webcam
     runs-on: ubuntu-20.04