CheckStructAlignments checks whether size and offsets of the C and Go
structs for the datapath match.
C struct size info is extracted from the given ELF object file debug section
encoded in DWARF.
To find a matching C struct field, a Go field has to be tagged with
`align:"field_name_in_c_struct". In the case of unnamed union field, such
union fields can be referred with special tags - `align:"$union0"`,
`align:"$union1"`, etc.