perf build: Pass O option to Makefile.perf in build-test

Unlike tools/perf/Makefile, tools/perf/Makefile.perf obey 'O' option
when it is passed through cmdline only, due to code in
tools/scripts/Makefile.include:

 ifneq ($(O),)
 ifeq ($(origin O), command line)
 	...
 	ABSOLUTE_O := $(shell cd $(O) ; pwd)
 	OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
 endif
 endif

This patch passes 'O' to Makefile.perf through cmdline explicitly
to make it follow O variable during build-test.

'make clean' should have identical 'O' option with 'make'. If not,
config-clean may error.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1452830421-77757-3-git-send-email-wangnan0@huawei.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>