perf record: Use sig_atomic_t for signal handlers

This removes undefined behavior as described in:

  https://wiki.sei.cmu.edu/confluence/display/c/SIG31-C.+Do+not+access+shared+objects+in+signal+handlersSuggested-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20221024181913.630986-3-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -646,10 +646,10 @@ static int record__pushfn(struct mmap *map, void *to, void *bf, size_t size)
 	return record__write(rec, map, bf, size);
 }
 
-static volatile int signr = -1;
-static volatile int child_finished;
+static volatile sig_atomic_t signr = -1;
+static volatile sig_atomic_t child_finished;
 #ifdef HAVE_EVENTFD_SUPPORT
-static volatile int done_fd = -1;
+static volatile sig_atomic_t done_fd = -1;
 #endif
 
 static void sig_handler(int sig)
@@ -1926,7 +1926,7 @@ static void record__read_lost_samples(struct record *rec)
 
 }
 
-static volatile int workload_exec_errno;
+static volatile sig_atomic_t workload_exec_errno;
 
 /*
  * evlist__prepare_workload will send a SIGUSR1