libbpf: Fix array comparison in BTF dedup

btf_dedup_identical_types() reads both array descriptors from t1,
skipping comparisons of their referenced types. This can incorrectly
merge distinct structs and corrupt CO-RE relocation metadata.

Read the second descriptor from t2.

Fixes: 62e23f183839 ("libbpf: Improve BTF dedup handling of "identical" BTF types")
Closes: https://lore.kernel.org/bpf/CABzjXVz3iBuump-pXFkefZ5v+2uu4fG61zqRyWD4xmz3PuBycw@mail.gmail.com/
Signed-off-by: Mingpei CAO <caomingpei@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260908164920.108074-2-caomingpei@gmail.com

src/btf.c

@@ -4831,7 +4831,7 @@ recur:
 			return false;
 
 		a1 = btf_array(t1);
-		a2 = btf_array(t1);
+		a2 = btf_array(t2);
 
 		if (a1->index_type != a2->index_type &&
 		    !btf_dedup_identical_types(d, a1->index_type, a2->index_type, depth - 1))