perf tools: Use asprintf() for simple string formatting/allocation

No need to use strbuf there, its just a simple alloc+formatting, which
asprintf does just fine.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-6q6cxfhk8c8ypg3tfpo0i2iy@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/perf.c

@@ -454,11 +454,12 @@ static void handle_internal_command(int argc, const char **argv)
 
 static void execv_dashed_external(const char **argv)
 {
-	struct strbuf cmd = STRBUF_INIT;
+	char *cmd;
 	const char *tmp;
 	int status;
 
-	strbuf_addf(&cmd, "perf-%s", argv[0]);
+	if (asprintf(&cmd, "perf-%s", argv[0]) < 0)
+		goto do_die;
 
 	/*
 	 * argv[0] must be the perf command, but the argv array
@@ -467,7 +468,7 @@ static void execv_dashed_external(const char **argv)
 	 * restore it on error.
 	 */
 	tmp = argv[0];
-	argv[0] = cmd.buf;
+	argv[0] = cmd;
 
 	/*
 	 * if we fail because the command is not found, it is
@@ -475,15 +476,16 @@ static void execv_dashed_external(const char **argv)
 	 */
 	status = run_command_v_opt(argv, 0);
 	if (status != -ERR_RUN_COMMAND_EXEC) {
-		if (IS_RUN_COMMAND_ERR(status))
+		if (IS_RUN_COMMAND_ERR(status)) {
+do_die:
 			die("unable to run '%s'", argv[0]);
+		}
 		exit(-status);
 	}
 	errno = ENOENT; /* as if we called execvp */
 
 	argv[0] = tmp;
-
-	strbuf_release(&cmd);
+	zfree(&cmd);
 }
 
 static int run_argv(int *argcp, const char ***argv)