In 5.2 kernel a new mechanism was introduced which embeds the kernel
headers in the kernel image and exposes them in procfs for simplified
use by userland tools.
It was introduced in
43d8ce9d65
and later modified a bit in
f7b101d330
The archive containing the header files had nondeterminism through the
header files metadata - specifically `mtime`, but I also decided to
normalize some other aspects just in case.
In our default setup we currently compile this as a module, so to expose
the headers to test the functionality `kheaders` needs to be loaded.
See https://lkml.org/lkml/2019/10/4/1036 and
https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=fixes&id=2cc99c9cdc8fde5e92e34f9655829449cebd3e00
I commented out the documentation part of the patch to make it cleanly apply to
5.2 and 5.3, see remark in the patch itself.
bdccffa81c