sync: Update libbpf submodule

Pull latest libbpf from mirror.
Libbpf version: 0.7.0
Libbpf commit:  fec0813359a9dd68dff7edb9f221b0f18d94433d
diff --git a/libbpf b/libbpf
index 3febb8a..fec0813 160000
--- a/libbpf
+++ b/libbpf
@@ -1 +1 @@
-Subproject commit 3febb8a16597f4605450f6c947f4deefb446cb8a
+Subproject commit fec0813359a9dd68dff7edb9f221b0f18d94433d