handle output of static libs

in numpy, for example:

```
Archive : wheel/numpy/core/lib/libnpymath.a
wheel/numpy/core/lib/libnpymath.a(npy_math.o):
wheel/numpy/core/lib/libnpymath.a(ieee754.o):
wheel/numpy/core/lib/libnpymath.a(npy_math_complex.o):
wheel/numpy/core/lib/libnpymath.a(halffloat.o):
```
Merge pull request #2 from minrk/archive-no-obj

MRG: handle output of static libs