perf tools: Add -lutil in python lib list for broken python-config

On some system the perf-config is broken, causes link failure like this:

   /usr/lib64/python2.7/config/libpython2.7.a(posixmodule.o): In function `posix_forkpty':
   /opt/wangnan/yocto-build/tmp-eglibc/work/x86_64-oe-linux/python/2.7.3-r0.3.1/Python-2.7.3/./Modules/posixmodule.c:3816: undefined reference to `forkpty'
   /usr/lib64/python2.7/config/libpython2.7.a(posixmodule.o): In function `posix_openpty':
   /opt/wangnan/yocto-build/tmp-eglibc/work/x86_64-oe-linux/python/2.7.3-r0.3.1/Python-2.7.3/./Modules/posixmodule.c:3756: undefined reference to `openpty'
   collect2: error: ld returned 1 exit status
  make[1]: *** [/home/wangnan/kernel-hydrogen/tools/perf/out/perf] Error 1
  make: *** [all] Error 2

  $ python-config --libs
  -lpthread -ldl -lpthread -lutil -lm -lpython2.7

In this case a '-lutil' should be appended to -lpython2.7.

(I know we have --start-group and --end-group. I can see them in command
line of collect2 by strace. However it doesn't work. Seems I have a
broken environment?)

Signed-off-by: Wang Nan <wangnan0@huawei.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/1452520124-2073-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/config/Makefile

@@ -493,7 +493,7 @@ else
 
       PYTHON_EMBED_LDOPTS := $(shell $(PYTHON_CONFIG_SQ) --ldflags 2>/dev/null)
       PYTHON_EMBED_LDFLAGS := $(call strip-libs,$(PYTHON_EMBED_LDOPTS))
-      PYTHON_EMBED_LIBADD := $(call grep-libs,$(PYTHON_EMBED_LDOPTS))
+      PYTHON_EMBED_LIBADD := $(call grep-libs,$(PYTHON_EMBED_LDOPTS)) -lutil
       PYTHON_EMBED_CCOPTS := $(shell $(PYTHON_CONFIG_SQ) --cflags 2>/dev/null)
       FLAGS_PYTHON_EMBED := $(PYTHON_EMBED_CCOPTS) $(PYTHON_EMBED_LDOPTS)