Backport validation support for composer-runtime-api (#8842)

Fixes #8841

src/Composer/Repository/PlatformRepository.php

@@ -27,7 +27,7 @@ use Symfony\Component\Process\ExecutableFinder;
  */
 class PlatformRepository extends ArrayRepository
 {
-    const PLATFORM_PACKAGE_REGEX = '{^(?:php(?:-64bit|-ipv6|-zts|-debug)?|hhvm|(?:ext|lib)-[a-z0-9](?:[_.-]?[a-z0-9]+)*|composer-plugin-api)$}iD';
+    const PLATFORM_PACKAGE_REGEX = '{^(?:php(?:-64bit|-ipv6|-zts|-debug)?|hhvm|(?:ext|lib)-[a-z0-9](?:[_.-]?[a-z0-9]+)*|composer-(?:plugin|runtime)-api)$}iD';
 
     private $versionParser;
 

tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php

@@ -86,6 +86,7 @@ class ValidatingArrayLoaderTest extends TestCase
                         'a/b' => '1.*',
                         'b/c' => '~2',
                         'example' => '>2.0-dev,<2.4-dev',
+                        'composer-runtime-api' => '*',
                     ),
                     'require-dev' => array(
                         'a/b' => '1.*',