kbuild: compile-test kernel headers to ensure they are self-contained

kbuild: compile-test kernel headers to ensure they are self-contained

The headers in include/ are globally used in the kernel source tree
to provide common APIs. They are included from external modules, too.

It will be useful to make as many headers self-contained as possible
so that we do not have to rely on a specific include order.

There are more than 4000 headers in include/. In my rough analysis,
70% of them are already self-contained. With efforts, most of them
can be self-contained.

For now, we must exclude more than 1000 headers just because they
cannot be compiled as standalone units. I added them to header-test-.
The blacklist was mostly generated by a script, so the reason of the
breakage should be checked later.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>