Remove dependency of libglaze on libelf

The dependency is onerous since it requires the user of Glaze to have
both a 32-bit and 64-bit development version of libelf available, (and
also have a toolchain ready to find either one as appropriate).

Meanwhile, the only thing we were doing with libelf was determining
whether the current library targets a 32-bit or a 64-bit
architecture. But we are compiling this code twice, once for each
architecture. So it is actually quite simple to just conditionally
compile in the value we want.