Fix library name and path on some 64bit systems

LIB_SUFFIX should be used for library directory suffix, not to make it part of library name
(eg. libswiftnav64.so)

If you intention was use it as suffix for library name (i does not recommend you to do this), then this suffix should be also added to all places where the library is used (-lswiftnav64 everywhere, at least tests are linked against -lswiftnav without suffix)