Use apt and absolute paths to force PHP 7.4

Author: alexeyabel

.github/workflows/tests.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Install system package dependencies
-        run: sudo apt-get update && sudo apt-get install composer php-sqlite3
+        run: sudo apt update && sudo apt install composer php-sqlite3
 
       - name: Checkout latest Nextcloud
         uses: actions/checkout@v2
@@ -28,8 +28,8 @@ jobs:
 
       - name: Install PHP dependencies with composer
         working-directory: ./nextcloud/apps/user_backend_sql_raw
-        run: composer install
+        run: php7.4 /usr/bin/composer install
 
       - name: Run all tests
         working-directory: ./nextcloud/apps/user_backend_sql_raw
-        run: vendor/phpunit/phpunit/phpunit
+        run: php7.4 ./vendor/phpunit/phpunit/phpunit