Merge branch 'Fix leaks in libbpf and selftests'

Andrii Nakryiko says:

====================

Fix all the memory leaks reported by ASAN. All but one are just improper
resource clean up in selftests. But one memory leak was discovered in libbpf,
leaving inner map's name leaked.

First patch fixes selftests' Makefile by passing through SAN_CFLAGS to linker.
Without that compiling with SAN_CFLAGS=-fsanitize=address kept failing.

Running selftests under ASAN in BPF CI is the next step, we just need to make
sure all the necessary libraries (libasan and liblsan) are installed on the
host and inside the VM. Would be great to get some help with that, but for now
make sure that test_progs run is clean from leak sanitizer errors.

v3->v4:
  - rebase on latest bpf-next;
v2->v3:
  - fix per-cpu array memory leaks in btf_iter.c selftests (Hengqi);
v1->v2:
  - call bpf_map__destroy() conditionally if map->inner_map is present.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>