Sync common files (CMakeLists.txt, Catch2) with main repo

This repo has its own set of common support files. it would be worthwhile to have them synced with [exericm/cpp](https://github.com/exercism/cpp)

See also https://github.com/exercism/cpp/issues/1029

将此仓库的 CMakeLists.txt 和 Catch2 支持文件与 exercism/cpp 仓库中对应的公共文件进行比较。阅读 exercism/cpp 的 issue 1029 以了解预期范围，然后同步这些文件，并验证测试运行器仍能构建并运行其测试。

由索引模型根据 Issue 内容生成。