refactor: replace SPC_LIBC with SPC_TARGET and update related logic

src/SPC/command/dev/EnvCommand.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SPC\command\dev;
+
+use SPC\command\BaseCommand;
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+#[AsCommand('dev:env', 'Returns the internally defined environment variables')]
+class EnvCommand extends BaseCommand
+{
+    public function configure()
+    {
+        $this->addArgument('env', InputArgument::REQUIRED, 'The environment variable to show, if not set, all will be shown');
+    }
+
+    public function initialize(InputInterface $input, OutputInterface $output): void
+    {
+        $this->no_motd = true;
+        parent::initialize($input, $output);
+    }
+
+    public function handle(): int
+    {
+        $env = $this->getArgument('env');
+        if (($val = getenv($env)) === false) {
+            $this->output->writeln("<error>Environment variable '{$env}' is not set.</error>");
+            return static::FAILURE;
+        }
+        $this->output->writeln("<info>{$val}</info>");
+        return static::SUCCESS;
+    }
+}

src/SPC/command/dev/PackLibCommand.php

@@ -16,6 +16,7 @@ use SPC\store\Config;
 use SPC\store\FileSystem;
 use SPC\store\LockFile;
 use SPC\util\DependencyUtil;
+use SPC\util\SPCTarget;
 use Symfony\Component\Console\Attribute\AsCommand;
 use Symfony\Component\Console\Input\InputArgument;
 
@@ -76,8 +77,12 @@ class PackLibCommand extends BuildCommand
                         '{name}' => $lib->getName(),
                         '{arch}' => arch2gnu(php_uname('m')),
                         '{os}' => strtolower(PHP_OS_FAMILY),
-                        '{libc}' => getenv('SPC_LIBC') ?: 'default',
-                        '{libcver}' => PHP_OS_FAMILY === 'Linux' ? (SystemUtil::getLibcVersionIfExists() ?? 'default') : 'default',
+                        '{libc}' => match (getenv('SPC_TARGET')) {
+                            SPCTarget::MUSL_STATIC, SPCTarget::MUSL => 'musl',
+                            SPCTarget::GLIBC => 'glibc',
+                            default => 'default',
+                        },
+                        '{libcver}' => SystemUtil::getLibcVersionIfExists() ?? 'default',
                     ];
                     // detect suffix, for proper tar option
                     $tar_option = $this->getTarOptionFromSuffix(Config::getPreBuilt('match-pattern'));