Build modified streamline images

The official image from streamline does not currently work for the arm64
platform. As a temporary measure, the source code and docker build scripts
have been lifted from the official images and are used to build locally.

Some additional modifications are made to reduce overall image size, these
are documented in docker/README.md

docker/streamline-src/vendor/phpunit/php-invoker/src/Invoker.php

@@ -0,0 +1,67 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-invoker.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace SebastianBergmann\Invoker;
+
+use const SIGALRM;
+use function call_user_func_array;
+use function function_exists;
+use function pcntl_alarm;
+use function pcntl_async_signals;
+use function pcntl_signal;
+use function sprintf;
+use Throwable;
+
+final class Invoker
+{
+    private int $timeout;
+
+    /**
+     * @throws Throwable
+     */
+    public function invoke(callable $callable, array $arguments, int $timeout): mixed
+    {
+        if (!$this->canInvokeWithTimeout()) {
+            throw new ProcessControlExtensionNotLoadedException(
+                'The pcntl (process control) extension for PHP is required'
+            );
+        }
+
+        pcntl_signal(
+            SIGALRM,
+            function (): void
+            {
+                throw new TimeoutException(
+                    sprintf(
+                        'Execution aborted after %d second%s',
+                        $this->timeout,
+                        $this->timeout === 1 ? '' : 's'
+                    )
+                );
+            },
+            true
+        );
+
+        $this->timeout = $timeout;
+
+        pcntl_async_signals(true);
+        pcntl_alarm($timeout);
+
+        try {
+            return call_user_func_array($callable, $arguments);
+        } finally {
+            pcntl_alarm(0);
+        }
+    }
+
+    public function canInvokeWithTimeout(): bool
+    {
+        return function_exists('pcntl_signal') && function_exists('pcntl_async_signals') && function_exists('pcntl_alarm');
+    }
+}