More small build fixes.  Switched to explicit 32-bit builds on all unix-y platforms as a more portable baseline.
More small build fixes.  Switched to explicit 32-bit builds on all
unix-y platforms as a more portable baseline.

patwonder/pbrt-v2-skin,patwonder/pbrt-v2-skin,patwonder/pbrt-v2-skin,patwonder/pbrt-v2-skin,patwonder/pbrt-v2-skin