Fix unsupported map linkage static.

[waruqi]

libbpf/bpftool#77
libbpf/bpftool#120
https://github.com/libbpf/libbpf-bootstrap/issues

[waruqi]

libbpf: map 'my_pid_map': unsupported map linkage static.
Error: failed to open BPF object file: Operation not supported

I have fixed this error.

We cannot add "-fvisibility=hidden" when compiling *.bpf.c in release mode. bpftool 7.2.0 cannot get map.

so I removed this flag in release mode.

Now we can use bpftool 7.2.0

[waruqi]

BTW, I have also fixed elfutils issue. #236

so please run following commands to fix all errors.

xrepo update-repo
xrepo remove --all -y elfutils
xmake f -p android -c
xmake

if you have not bpftool,

you can run

xmake f -p android -c --require-bpftool=y