Merge git://git.kernel.org/pub/scm/linux/kernel/git/sam/kbuild

* git://git.kernel.org/pub/scm/linux/kernel/git/sam/kbuild:
  kbuild: explain why DEBUG_SECTION_MISMATCH is UNDEFINED
  kbuild: fix building vmlinux.o
  kbuild: allow -fstack-protector to take effect
  kconfig: fix select in combination with default