perf bench futex: Add missing stdbool.h

futex.h uses bool but lacks stdbool.h which causes build failures in
some build systems. Add the missing #include.

Signed-off-by: Ian Rogers <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: André Almeida <[e-mail]>
Cc: Daniel Borkmann <[e-mail]>
Cc: Darren Hart <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: Davidlohr Bueso <[e-mail]>
Cc: Ido Schimmel <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jakub Kicinski <[e-mail]>
Cc: Jamal Hadi Salim <[e-mail]>
Cc: Jason Xing <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Jonas Gottlieb <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Maurice Lambert <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paolo Abeni <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Petr Machata <[e-mail]>
Cc: Rasmus Villemoes <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Yury Norov <[e-mail]>
Cc: Yuyang Huang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/bench/futex.h

···
 #ifndef _FUTEX_H
 #define _FUTEX_H
 
+#include <stdbool.h>
 #include <unistd.h>
 #include <sys/syscall.h>
 #include <sys/types.h>