selftests/bpf: Add btf_dump__new to test_cpp

Adding btf_dump__new call to test_cpp, so we can
test C++ compilation with that.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211223131736.483956-2-jolsa@kernel.org

tools/testing/selftests/bpf/test_cpp.cpp

@@ -7,9 +7,15 @@
 
 /* do nothing, just make sure we can link successfully */
 
+static void dump_printf(void *ctx, const char *fmt, va_list args)
+{
+}
+
 int main(int argc, char *argv[])
 {
+	struct btf_dump_opts opts = { };
 	struct test_core_extern *skel;
+	struct btf *btf;
 
 	/* libbpf.h */
 	libbpf_set_print(NULL);
@@ -18,7 +24,8 @@ int main(int argc, char *argv[])
 	bpf_prog_get_fd_by_id(0);
 
 	/* btf.h */
-	btf__new(NULL, 0);
+	btf = btf__new(NULL, 0);
+	btf_dump__new(btf, dump_printf, nullptr, &opts);
 
 	/* BPF skeleton */
 	skel = test_core_extern__open_and_load();