Avoid unexpected linker messages "Conflicting CPU architectures 13/0"

Fixes #61

The root cause of the issue is that the linker is assuming the wrong
defaults for an object which does not have a .ARM.attributes section.

We can remove all ".ARM.attributes " before linking to avoid this noise.
Please reference
http://permalink.gmane.org/gmane.comp.gnu.binutils/54317
Merge pull request #68 from georgekang/master

avoid unexpected linker message "Conflicting CPU architectures 13/0"