Install libbpf in update_codegen_tests.sh
Install libbpf in update_codegen_tests.sh

Since libbpf is now required, it has to be installed in the container
when doing codegen update, otherwise bpftrace does not compile.

iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace