Harden smali folder name validation during build to prevent path traversal

[Copilot]

Directories named smali_<suffix> in decoded projects are converted to dex output paths by replacing @ with the platform path separator. A malicious directory name like smali_..@..@..@outside produces ../../../outside.dex, enabling arbitrary file writes outside the build output directory.

Changes

• ApkBuilder.java: After computing fileName from a smali_ directory name, validate the derived path using the existing BrutIO.sanitizePath(outDir, fileName). Throws AndrolibException if the resolved path escapes outDir.

} else if (dirName.startsWith("smali_")) {
    fileName = dirName.substring(dirName.indexOf('_') + 1).replace('@', File.separatorChar) + ".dex";
    try {
        BrutIO.sanitizePath(outDir, fileName);
    } catch (InvalidPathException | IOException ex) {
        throw new AndrolibException("Smali folder name leads to invalid dex path: "
            + dirName + " -> " + fileName, ex);
    }
}

• SmaliDirectoryTraversalTest.java (new): Verifies that building a project containing a smali_..@..@..@outside directory throws AndrolibException rather than writing files outside the project.

• Fixes Harden "smali" folder during build #4181