perf tools: Fix building error for arm64.

Commit b11db658 ("perf tools: Fix build
error on ARCH=i386/x86_64/sparc64") uses sed on ARCH, which triggers a
bug in sequence of sed expression, where 's/arm.*/arm/' will replace
'arm64' to 'arm', causes arm64 building failure.

This patch prevent 'arm64' to be mached for 'arm.*' case.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1426598987-75245-1-git-send-email-wangnan0@huawei.com


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