[][openwrt][common][sdk][Add support to generate compile_commands.json for clangd]

[Description]
Add support to generate compile_commands.json of kernel, kernel modules
and packages for clangd.

[Release-log]
N/A

Change-Id: I458a19adf23c68dd45f9fbff83c7c51fdb6ab45e
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8202712
3 files changed