* add ability to export autoremove .la files

https://github.com/conda/conda-build/issues/16

auto-remove linux .la files

if one builds more apps **within the conda framework** like gmp, mpfr, gcc, glibc and the whole essential development apps one might run into a number of issues
one of them might be: .la

example of conda build gmp .la

libgmp.la

```
...
...

# Directory that this library needs to be installed in:
libdir='/opt/anaconda1anaconda2anaconda3/lib'
```

one can read more for instance here: http://www.metastatic.org/text/libtool.html

to avoid removing them individually I did a small function in conda-build