Fixed unused shared libraries

[NicoHood]

Fixes:

$ ldd -u -r _snowboydetect.so 
Unused direct dependencies:
	/usr/lib/libdl.so.2
	/usr/lib/libutil.so.1
	/usr/lib/liblapack.so.3

This might be worth to add also on other Makefiles. I did not test them though.

[chenguoguo]

Thanks! I'll test and merge when I have a linux machine by hand.