kbuild: Add support for an "archheaders" target

Add support for an "archheaders" target.  This target can generate
files that need to be installed for user space by "make
headers_install" or "make headers_install_all".

In order to support "make headers_install_all", it must be able to run
without the tree having to be configured first.

Cc: David Woodhouse <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Cc: Michal Marek <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
3 files changed