fix: PHPUnit test Process() format

\Symfony\Component\Process\Process refuses being passed a string
with version > 5, which is installed with PHP > 7.2.5.

It also refuses being passed an array with version < 3.3, which is
installed with PHP < 5.5.9.

Solved by checking if Process::fromShellCommandLine() exists, which
was introduced in version 4.2.0.

tests/PhpWord/_includes/AbstractWebServerEmbeddedTest.php

@@ -26,7 +26,26 @@ abstract class AbstractWebServerEmbeddedTest extends \PHPUnit\Framework\TestCase
     public static function setUpBeforeClass()
     {
         if (self::isBuiltinServerSupported()) {
-            self::$httpServer = new Process('php -S localhost:8080 -t tests/PhpWord/_files');
+            $commandLine = 'php -S localhost:8080 -t tests/PhpWord/_files';
+
+            /*
+             * Make sure to invoke \Symfony\Component\Process\Process correctly
+             * regardless of PHP version used.
+             *
+             * In Process version >= 5 / PHP >= 7.2.5, the constructor requires
+             * an array, while in version < 3.3 / PHP < 5.5.9 it requires a string.
+             * In between, it can accept both.
+             *
+             * Process::fromShellCommandLine() was introduced in version 4.2.0,
+             * to enable recent versions of Process to parse a command string,
+             * so if it is not available it means it is still possible to pass
+             * a string to the constructor.
+             */
+            if (method_exists('Symfony\Component\Process\Process', 'fromShellCommandLine')) {
+                self::$httpServer = Process::fromShellCommandline($commandLine);
+            } else {
+                self::$httpServer = new Process($commandLine);
+            }
             self::$httpServer->start();
             while (!self::$httpServer->isRunning()) {
                 usleep(1000);