This is only necessary in cases where the build compiler uses different built-in include paths than clang (specifically, the clang from the same package as clangd) does -- usually, cross-compilation setups (e.g. build compiler targets embedded environment), but could be some others (e.g. ...
Current versions of the script extract the archives from Windows and write the necessary NTFS extended attributes for WSL at the same time. This is less errorprone, and does not require a working rootfs to be present. In case you get errors with the newer versions, open%LocalAppData%\lxss...