perf tools: Fix phony build target for build-test

make_kernelsrc and make_kernelsrc_tools are skiped if a previous
build-test is done, because 'make build-test' creates two files with
same names. To avoid this, they should be included in .PHONY list.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: 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/1452520124-2073-3-git-send-email-wangnan0@huawei.com


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