bpf, libbpf: fix version info and add it to shared object
Even though libbpf's versioning script for the linker (libbpf.map)
is pointing to 0.0.2, the BPF_EXTRAVERSION in the Makefile has
not been updated along with it and is therefore still on 0.0.1.
While fixing up, I also noticed that the generated shared object
versioning information is missing, typical convention is to have
a linker name (libbpf.so), soname (libbpf.so.0) and real name
(libbpf.so.0.0.2) for library management. This is based upon the
LIBBPF_VERSION as well.
The build will then produce the following bpf libraries:
# rm -rf /tmp/bld; mkdir /tmp/bld; make -j$(nproc) O=/tmp/bld install
Auto-detecting system features:
... libelf: [ on ]
... bpf: [ on ]
CC /tmp/bld/libbpf.o
CC /tmp/bld/bpf.o
CC /tmp/bld/nlattr.o
CC /tmp/bld/btf.o
CC /tmp/bld/libbpf_errno.o
CC /tmp/bld/str_error.o
CC /tmp/bld/netlink.o
CC /tmp/bld/bpf_prog_linfo.o
CC /tmp/bld/libbpf_probes.o
CC /tmp/bld/xsk.o
LD /tmp/bld/libbpf-in.o
LINK /tmp/bld/libbpf.a
LINK /tmp/bld/libbpf.so.0.0.2
LINK /tmp/bld/test_libbpf
INSTALL /tmp/bld/libbpf.a
INSTALL /tmp/bld/libbpf.so.0.0.2