create and link as a static library

[mmaroti]

First of all, thanks for doing the rust binding for the cryptominisat. I am experimenting with it and I run into a problem that my generated binary dynamically links to the cryptominisat and when I run it I get the following error:

error while loading shared libraries: libcryptominisat5.so.5.6: cannot open shared object file: No such file or directory

Of course if I add the LD_LIBRARY_PATH the generated library file then everything is OK, but I would like to avoid that. Is it possible to statically link against the cryptominisat library?