PHP 8.1: fix Phar building

For the time being, until box-project/box#567 has been fixed:
1. Disable the addition of the requirement checker from Box as the version included in the last release of Box is not compatible with PHP 8.1.
2. Change the PHP version used to generate the Phar to PHP 8.0 to get round the problem the PHP compactor has with attributes.
    Note: the generated Phar file should still be compatible with all supported PHP versions.

.github/workflows/release.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 7.3
+          php-version: 8.0
           extensions: exif, phar, openssl
           coverage: none
           ini-values: phar.readonly=Off

.github/workflows/test.yml

@@ -45,7 +45,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 7.3
+          php-version: 8.0
           extensions: exif, phar, openssl
           coverage: none
           tools: phive

box.json

@@ -2,6 +2,7 @@
     "base-path": null,
     "output": "parallel-lint.phar",
     "chmod": "0755",
+    "check-requirements": false,
     "compactors": [
         "KevinGH\\Box\\Compactor\\Php"
     ],