Add new tests, remove redundant code

tests/SPC/builder/linux/SystemUtilTest.php

@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SPC\Tests\builder\linux;
+
+use PHPUnit\Framework\TestCase;
+use SPC\builder\linux\SystemUtil;
+
+/**
+ * @internal
+ */
+class SystemUtilTest extends TestCase
+{
+    public static function setUpBeforeClass(): void
+    {
+        if (PHP_OS_FAMILY !== 'Linux') {
+            self::markTestIncomplete('This test is only for Linux');
+        }
+    }
+
+    public function testIsMuslDistAndGetOSRelease()
+    {
+        $release = SystemUtil::getOSRelease();
+        // we cannot ensure what is the current distro, just test the key exists
+        $this->assertArrayHasKey('dist', $release);
+        $this->assertArrayHasKey('ver', $release);
+        $this->assertTrue($release['dist'] === 'alpine' && SystemUtil::isMuslDist() || $release['dist'] !== 'alpine' && !SystemUtil::isMuslDist());
+    }
+
+    public function testFindStaticLib()
+    {
+        $this->assertIsArray(SystemUtil::findStaticLib('ld-linux-x86-64.so.2'));
+    }
+
+    public function testGetCpuCount()
+    {
+        $this->assertIsInt(SystemUtil::getCpuCount());
+    }
+
+    public function testFindHeader()
+    {
+        $this->assertIsArray(SystemUtil::findHeader('elf.h'));
+    }
+
+    public function testGetCrossCompilePrefix()
+    {
+        $this->assertIsString(SystemUtil::getCrossCompilePrefix('gcc', 'x86_64'));
+    }
+
+    public function testGetCCType()
+    {
+        $this->assertEquals('gcc', SystemUtil::getCCType('xjfoiewjfoewof-gcc'));
+    }
+
+    public function testGetSupportedDistros()
+    {
+        $this->assertIsArray(SystemUtil::getSupportedDistros());
+    }
+
+    public function testFindHeaders()
+    {
+        $this->assertIsArray(SystemUtil::findHeaders(['elf.h']));
+    }
+
+    public function testFindStaticLibs()
+    {
+        $this->assertIsArray(SystemUtil::findStaticLibs(['ld-linux-x86-64.so.2']));
+    }
+}