Attempt to suppress deprecation warnings in main CLI process

The STDERR of the main process should be stable, but PHP deprecations (and their flawed
design) make it really challenging to operate with them dependant on PHP defaults.

We therefore force them to be off.

Deprecations affecting us on PHP 8.5, right now:

* revoltphp/event-loop#114
* revoltphp/event-loop#110
* symfony/symfony#61772

Author: Ocramius

bin/roave-backward-compatibility-check.php

@@ -34,9 +34,15 @@
 use Symfony\Component\Console\Input\ArgvInput;
 use Symfony\Component\Console\Output\ConsoleOutput;
 
+use function error_reporting;
 use function file_exists;
 
+use const E_ALL;
+use const E_DEPRECATED;
+
 (static function (): void {
+    error_reporting(E_ALL & ~E_DEPRECATED);
+
     (static function (): void {
         $autoloaderLocations = [
             __DIR__ . '/../vendor/autoload.php', // Installed by cloning the project and running `composer install`