[ifs] Add --strip-size flag

[ifs] Add --strip-size flag

st_size may not be of importance to the abi if you are not using
copy relocations. This is helpful when you want to check the abi
of a shared object both when instrumented and not because asan
will increase the size of objects to include the redzone.

Differential revision: https://reviews.llvm.org/D124792