[PATCH bpf 2/2] samples: bpf: fix 'unknown warning group' build warning on Clang

Clang doesn't have 'stringop-truncation' group like GCC does, and
complains about it when building samples which use xdp_sample_user
infra:

 samples/bpf/xdp_sample_user.h:48:32: warning: unknown warning group '-Wstringop-truncation', ignored [-Wunknown-warning-option]
 #pragma GCC diagnostic ignored "-Wstringop-truncation"
                                ^
[ repeat ]

Those are harmless, but avoidable when guarding it with ifdef.
I could guard push/pop as well, but this would require one more
ifdef cruft around a single line which I don't think is reasonable.

Fixes: 156f886cf697 ("samples: bpf: Add basic infrastructure for XDP samples")
Signed-off-by: Alexander Lobakin <redacted>
---
 samples/bpf/xdp_sample_user.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/samples/bpf/xdp_sample_user.h b/samples/bpf/xdp_sample_user.h
index d97465ff8c62..5f44b877ecf5 100644
--- a/samples/bpf/xdp_sample_user.h
+++ b/samples/bpf/xdp_sample_user.h

@@ -45,7 +45,9 @@ const char *get_driver_name(int ifindex);
 int get_mac_addr(int ifindex, void *mac_addr);
 
 #pragma GCC diagnostic push
+#ifndef __clang__
 #pragma GCC diagnostic ignored "-Wstringop-truncation"
+#endif
 __attribute__((unused))
 static inline char *safe_strncpy(char *dst, const char *src, size_t size)
 {

-- 
2.33.1