tools build feature: Check if pthread_barrier_t is available

As 'perf bench futex wake-parallel" will use this, which is not
available in older systems such as versions of the android NDK used in
my container build tests (r12b and r15c at the moment).

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: James Yang <james.yang@arm.com
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kim Phillips <kim.phillips@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-1i7iv54in4wj08lwo55b0pzv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>