Pull kbuild regression fix from Michal Marek:
 "The problem is that commit 9c8fa9bc08f6 ("kbuild: fix if_change and
  friends to consider argument order") fixed a potential missed rebuild,
  but this results in unnnecessary rebuilds with the packaging targets.
  Which is still more correct than the previous logic, but also very
  annoying"

* 'rc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild: Initialize exported variables

The NOSTDINC_FLAGS variable is exported, so it needs to be cleared to
avoid duplicating its content when running make from within make (e.g.
in the packaging targets). This became an issue after commit
9c8fa9bc08f6 ("kbuild: fix if_change and friends to consider argument
order"), which no longer ignores the duplicate options. As Paulo Zanoni
points out, the LDFLAGS_vmlinux variable has the same problem.

Reported-by: "Zanoni, Paulo R" <paulo.r.zanoni@intel.com>
Fixes: 9c8fa9bc08f6 ("kbuild: fix if_change and friends to consider argument order")
Signed-off-by: Michal Marek <mmarek@suse.com>