btrfs-tools was failing occasionally due to version.h being missing. This
fixes the problems, thanks to several people on #yocto for helping out
why my lack of make knowledge of old fashioned suffix rules :)
(From OE-Core rev: 7be8010186889cece97829025d97d94f21c1f2e5)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>