Backport Laravel test hack

The way to work around this changed, backport the version from
master.

azure/community_job.yml

@@ -52,10 +52,11 @@ jobs:
         cd framework
         php7.4 /usr/bin/composer install --no-progress
         export USE_ZEND_ALLOC=0
-        sed -i 's/$exit = true/$exit = false/g' vendor/phpunit/phpunit/src/TextUI/Command.php
         # Avoid test using exit(), which thus leaks.
         # We can use USE_TRACKED_ALLOC=1 if more of these show up.
-        sed -i "s/function_exists('pcntl_fork')/false/" tests/Filesystem/FilesystemTest.php
+        sed -i 's/$exit = true/$exit = false/g' vendor/phpunit/phpunit/src/TextUI/Command.php
+        # Hack to disable a test that hangs on azure
+        sed -i 's/PHP_OS/"Darwin"/' tests/Filesystem/FilesystemTest.php
         php vendor/bin/phpunit
       displayName: 'Test Laravel'
     - script: |