Allow building and installing static lib
Allow building and installing static lib

Refactored the install rules a bit, so that installing the static
lib optionally becomes a bit more convenient.

iblumenfeld/libntru,jl777/libntru,jquesnelle/libntru,jquesnelle/libntru,jl777/libntru,iblumenfeld/libntru,iblumenfeld/libntru,jquesnelle/libntru,jl777/libntru