refactor: replace SPC_LIBC with SPC_TARGET and update related logic

src/SPC/util/toolchain/ToolchainInterface.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SPC\util\toolchain;
+
+interface ToolchainInterface
+{
+    /**
+     * Initialize the environment for the given target.
+     */
+    public function initEnv(string $target): void;
+
+    /**
+     * Perform actions after the environment has been initialized for the given target.
+     */
+    public function afterInit(string $target): void;
+}