perf record: Improve 'Workload failed' message printing events + what was exec'ed

Before:

  # perf record -a cycles,instructions,cache-misses
  Workload failed: No such file or directory
  #

After:

  # perf record -a cycles,instructions,cache-misses
  Failed to collect 'cycles' for the 'cycles,instructions,cache-misses' workload: No such file or directory
  #

Helps disambiguating other error scenarios:

  # perf record -a -e cycles,instructions,cache-misses bla
  Failed to collect 'cycles,instructions,cache-misses' for the 'bla' workload: No such file or directory
  # perf record -a cycles,instructions,cache-misses sleep 1
  Failed to collect 'cycles' for the 'cycles,instructions,cache-misses' workload: No such file or directory
  #

When all goes well we're back to the usual:

  # perf record -a -e cycles,instructions,cache-misses sleep 1
  [ perf record: Woken up 3 times to write data ]
  [ perf record: Captured and wrote 3.151 MB perf.data (21242 samples) ]
  #
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20210414131628.2064862-3-acme@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -1977,9 +1977,13 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 		record__auxtrace_snapshot_exit(rec);
 
 	if (forks && workload_exec_errno) {
-		char msg[STRERR_BUFSIZE];
+		char msg[STRERR_BUFSIZE], strevsels[2048];
 		const char *emsg = str_error_r(workload_exec_errno, msg, sizeof(msg));
-		pr_err("Workload failed: %s\n", emsg);
+
+		evlist__scnprintf_evsels(rec->evlist, sizeof(strevsels), strevsels);
+
+		pr_err("Failed to collect '%s' for the '%s' workload: %s\n",
+			strevsels, argv[0], emsg);
 		err = -1;
 		goto out_child;
 	}