v4.5-rc1 of the kernel splits the subcommand related files
from perf into a new library, this patch adds the modification
of the Makefile to preserve the --sysroot option as for
the other perf related Makefiles.
(From OE-Core rev: e46eae34ac71d28aa92feed369c2d92248ed3e19)
Signed-off-by: Martin Donnelly <martin.donnelly@ge.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>