Add a missing step.

Author: johnbillion

.github/workflows/reusable-phpunit-tests-v1.yml

@@ -50,6 +50,7 @@ on:
         type: boolean
         default: false
 env:
+  COMPOSER_INSTALL: ${{ false }}
   LOCAL_PHP: ${{ inputs.php }}-fpm
   LOCAL_PHPUNIT: ${{ inputs.phpunit && inputs.phpunit || inputs.php }}-fpm
   LOCAL_PHP_MEMCACHED: ${{ inputs.memcached }}
@@ -111,6 +112,11 @@ jobs:
       - name: Build WordPress
         run: npm run build
 
+      - name: Get composer cache directory
+        if: ${{ env.COMPOSER_INSTALL == true }}
+        id: composer-cache
+        run: echo composer_dir="$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
+
       - name: Cache Composer dependencies
         if: ${{ env.COMPOSER_INSTALL == true }}
         uses: actions/cache@6849a6489940f00c2f30c0fb92c6274307ccb58a # v4.1.2