perf build: Pass O option to kernel makefile in build-test

perf build: Pass O option to kernel makefile in build-test

Kernel makefile only follows an 'O' option passed from command line
explicitely. In build-test with 'O' option set, kernel makefile
contaminate kernel source directory. Build test also fail if we don't
create output directory manually.

K_O_OPT is added and passed to kernel makefile if 'O' is passed
to build-test.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1452830421-77757-5-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>