get correct filename when analyzing

[dtcccc]

In bpf, the assert in boundary/analyze.py:
assert (key, file) not in local_sympos
will be hit when key='__bpf_prog_run_save_cb' and file='include/linux/filter.h'

However, this key is in different c files (e.g., kernel/bpf/cgroup.c and net/core/filter.c). But analyze.py get the filename as filter.h