Finish the translation of kbuild/headers_install.rst and
kbuild/index.rst, then add kbuild into zh_CN/index.rst.

Update to commit 5b67fbfc ("Merge tag 'kbuild-v5.7' of
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild")
Signed-off-by: Dongliang Mu <dzm91@hust.edu.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
[jc: added missing EOF newline ]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240726145754.2598197-1-dzm91@hust.edu.cn