selftests/exec: Use %zu to format size_t

On 32-bit:

execveat.c: In function 'check_execveat_pathmax':
execveat.c:183: warning: format '%lu' expects type 'long unsigned int', but argument 3 has type 'size_t'
execveat.c:187: warning: format '%lu' expects type 'long unsigned int', but argument 2 has type 'size_t'

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/exec/execveat.c

@@ -179,11 +179,11 @@ static int check_execveat_pathmax(int dot_dfd, const char *src, int is_script)
 	 */
 	fd = open(longpath, O_RDONLY);
 	if (fd > 0) {
-		printf("Invoke copy of '%s' via filename of length %lu:\n",
+		printf("Invoke copy of '%s' via filename of length %zu:\n",
 			src, strlen(longpath));
 		fail += check_execveat(fd, "", AT_EMPTY_PATH);
 	} else {
-		printf("Failed to open length %lu filename, errno=%d (%s)\n",
+		printf("Failed to open length %zu filename, errno=%d (%s)\n",
 			strlen(longpath), errno, strerror(errno));
 		fail++;
 	}