[PATCH bpf] selftests/bpf: Fix broken build where char is unsigned

[Björn Töpel <bjorn@xxxxxxxxxx>]

From: Björn Töpel <bjorn@xxxxxxxxxxxx>

There are architectures where char is not signed. If so, the following
error is triggered:

  | xdp_hw_metadata.c:435:42: error: result of comparison of constant -1 \
  |   with expression of type 'char' is always true \
  |   [-Werror,-Wtautological-constant-out-of-range-compare]
  |   435 |         while ((opt = getopt(argc, argv, "mh")) != -1) {
  |       |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~
  | 1 error generated.

Correct by changing the char to int.

Fixes: bb6a88885fde ("selftests/bpf: Add options and frags to xdp_hw_metadata")
Signed-off-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
---
 tools/testing/selftests/bpf/xdp_hw_metadata.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
index 17c0f92ff160..c3ba40d0b9de 100644
--- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
+++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
@@ -430,7 +430,7 @@ static void print_usage(void)
 
 static void read_args(int argc, char *argv[])
 {
-	char opt;
+	int opt;
 
 	while ((opt = getopt(argc, argv, "mh")) != -1) {
 		switch (opt) {

base-commit: cb3c6a58be50c65014296aa3455cae0fa1e82eac
-- 
2.40.1