LU-5941 build: build dkms build at installed source tree

LU-5941 build: build dkms build at installed source tree

Port from:
https://github.com/
zfsonlinux/zfs/commit/46bf86a9635266dd399443f5bf5c5f8d0f280aa2

Signed-off-by: Minh Diep <minh.diep@intel.com>
Change-Id: If0c8543d955594b4f9dc305c35271a9cc94e1bbd
Reviewed-on: http://review.whamcloud.com/12802
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>