Add new tests, remove redundant code

tests/SPC/builder/macos/SystemUtilTest.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SPC\Tests\builder\macos;
+
+use PHPUnit\Framework\TestCase;
+use SPC\builder\macos\SystemUtil;
+
+/**
+ * @internal
+ */
+class SystemUtilTest extends TestCase
+{
+    public static function setUpBeforeClass(): void
+    {
+        if (PHP_OS_FAMILY !== 'Darwin') {
+            self::markTestIncomplete('This test is only for macOS');
+        }
+    }
+
+    public function testGetCpuCount()
+    {
+        $this->assertIsInt(SystemUtil::getCpuCount());
+    }
+
+    public function testGetArchCFlags()
+    {
+        $this->assertEquals('--target=x86_64-apple-darwin', SystemUtil::getArchCFlags('x86_64'));
+    }
+}