This adds a BPF program with a ring buffer and an associated test that
ensures the program and ring buffer can be loaded by the bpf loader. In
the following changes, this foundation will be used to test the user
space ring buffer wrapper class.
Unlike BpfMap, userspace can't (easily) write to the ring buffer so the
most accurate way to test a userspace ring buffer implementation is to
write to it from a BPF program.
Note: the BPF program in this change is never actually attached to a
cgroup, it is only loaded. The program will be executed manually using
BPF_PROG_RUN which is "side-effect free" (it can have side effects on
BPF maps, but not on Kernel state, e.g. dropping packets).
Bug: 246985031
Test: atest libbpf_android_test
Change-Id: Ib9c591218188f5f358a755c8854bc6f87d26af12
