perf probe: Build error with missing libraries

[Arnaldo Carvalho de Melo <acme@ghostprotocols.net>]

On a Ubuntu system just installed (13.10, x86_64), I'm installing the
devel libs one by one to check if there are problems with the automatic
disabling of features that requires libraries not installed.

Stumbled at this:

  CC       /tmp/build/perf/util/probe-event.o
util/probe-event.c: In function ‘try_to_find_probe_trace_events’:
util/probe-event.c:753:46: error: unused parameter ‘target’
[-Werror=unused-parameter]
     int max_tevs __maybe_unused, const char *target)
                                              ^
util/probe-event.c: At top level:
util/probe-event.c:193:12: error: ‘get_text_start_address’ defined but
not used [-Werror=unused-function]
 static int get_text_start_address(const char *exec, unsigned long
*address)
            ^
cc1: all warnings being treated as errors
make[1]: *** [/tmp/build/perf/util/probe-event.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [install] Error 2
make: Leaving directory `/home/acme/git/linux/tools/perf'
acme@ubuntu13:~/git/linux$ 

Investigating...

- Arnaldo