Bump PHP minimum requirement to 8.0

PHPStan failed on 7.4 after updating to 0.12.99, and I figured it was less hassle to just do this than fix the build. In any case, we stopped shipping 7.4 months ago, and warned at 3.22 release that 7.4 support would soon be dropped.

BUILDING.md

@@ -2,13 +2,13 @@
 ## Pre-requisites
 - A bash shell (git bash is sufficient for Windows)
 - [`git`](https://git-scm.com) available in your shell
-- PHP 7.4 or newer available in your shell
+- PHP 8.0 or newer available in your shell
 - [`composer`](https://getcomposer.org) available in your shell
 
 ## Custom PHP binaries
 Because PocketMine-MP requires several non-standard PHP extensions and configuration, PMMP provides scripts to build custom binaries for running PocketMine-MP, as well as prebuilt binaries.
 
-- [Prebuilt binaries](https://jenkins.pmmp.io/job/PHP-7.4-Aggregate)
+- [Prebuilt binaries](https://jenkins.pmmp.io/job/PHP-8.0-Aggregate)
 - [Compile scripts](https://github.com/pmmp/php-build-scripts) are provided as a submodule in the path `build/php`
 
 If you use a custom binary, you'll need to replace `composer` usages in this guide with `path/to/your/php path/to/your/composer.phar`.
@@ -38,7 +38,7 @@ There is a bug in PHP that might cause an error which looks like this:
 ```
 Fatal error: Uncaught BadMethodCallException: unable to create temporary file in PocketMine-MP/build/server-phar.php:119
 ```
-You can work around it by setting `ulimit -n` to some bigger number, e.g. `8192`, or by updating your PHP version to at least 7.4.16 or 8.0.3.
+You can work around it by setting `ulimit -n` to some bigger number, e.g. `8192`, or by updating your PHP version to at least 8.0.3.
 
 ## Running PocketMine-MP from source code
 Run `src/pocketmine/PocketMine.php` using your preferred PHP binary.